Movatterモバイル変換

Changelog

Added in version 2.2:Moved fromflask.url_for, which calls this method.

make_response(rv)¶

Convert the return value from a view function to an instance ofresponse_class.

Parameters:

rv (ft.ResponseReturnValue) –

the return value from the view function. The view functionmust return a response. ReturningNone, or the view endingwithout returning, is not allowed. The following types are allowedforview_rv:

str: A response object is created with the string encoded to UTF-8as the body.
bytes: A response object is created with the bytes as the body.
dict: A dictionary that will be jsonify’d before being returned.
list: A list that will be jsonify’d before being returned.
generator oriterator: A generator that returnsstr orbytes to bestreamed as the response.
tuple: Either(body,status,headers),(body,status), or(body,headers), wherebody is any of the other typesallowed here,status is a string or an integer, andheaders is a dictionary or a list of(key,value)tuples. Ifbody is aresponse_class instance,status overwrites the exiting value andheaders areextended.
response_class: The object is returned unchanged.
otherResponse class: The object is coerced toresponse_class.
callable(): The function is called as a WSGI application. The result isused to create a response object.

Return type:

Changelog

Changed in version 2.2:A generator will be converted to a streaming response.A list will be converted to a JSON response.

Changed in version 1.1:A dict will be converted to a JSON response.

Changed in version 0.9:Previously a tuple was interpreted as the arguments for theresponse object.

preprocess_request()¶

Called before the request is dispatched. Callsurl_value_preprocessors registered with the app and thecurrent blueprint (if any). Then callsbefore_request_funcsregistered with the app and the blueprint.

If anybefore_request() handler returns a non-None value, thevalue is handled as if it was the return value from the view, andfurther request handling is stopped.

Return type:: ft.ResponseReturnValue | None

process_response(response)¶

Can be overridden in order to modify the response objectbefore it’s sent to the WSGI server. By default this willcall all theafter_request() decorated functions.

Changelog

Changed in version 0.5:As of Flask 0.5 the functions registered for after requestexecution are called in reverse order of registration.

Parameters:: response (Response) – aresponse_class object.
Returns:: a new response object or the same, has to be aninstance ofresponse_class.
Return type:: Response

do_teardown_request(exc=_sentinel)¶

Called after the request is dispatched and the response isreturned, right before the request context is popped.

This calls all functions decorated withteardown_request(), andBlueprint.teardown_request()if a blueprint handled the request. Finally, therequest_tearing_down signal is sent.

This is called byRequestContext.pop(),which may be delayed during testing to maintain access toresources.

Parameters:: exc (BaseException |None) – An unhandled exception raised while dispatching therequest. Detected from the current exception information ifnot passed. Passed to each teardown function.
Return type:: None

Changelog

Changed in version 0.9:Added theexc argument.

do_teardown_appcontext(exc=_sentinel)¶

Called right before the application context is popped.

When handling a request, the application context is poppedafter the request context. Seedo_teardown_request().

This calls all functions decorated withteardown_appcontext(). Then theappcontext_tearing_down signal is sent.

This is called byAppContext.pop().

Changelog

Added in version 0.9.

Parameters:: exc (BaseException |None)
Return type:: None

app_context()¶

Create anAppContext. Use as awithblock to push the context, which will makecurrent_apppoint at this application.

An application context is automatically pushed byRequestContext.push()when handling a request, and when running a CLI command. Usethis to manually create a context outside of these situations.

withapp.app_context():init_db()

SeeThe Application Context.

Changelog

Added in version 0.9.

Return type:: AppContext

request_context(environ)¶

Create aRequestContext representing aWSGI environment. Use awith block to push the context,which will makerequest point at this request.

SeeThe Request Context.

Typically you should not call this from your own code. A requestcontext is automatically pushed by thewsgi_app() whenhandling a request. Usetest_request_context() to createan environment and context instead of this method.

Parameters:: environ (WSGIEnvironment) – a WSGI environment
Return type:: RequestContext

test_request_context(*args,**kwargs)¶

Create aRequestContext for a WSGIenvironment created from the given values. This is mostly usefulduring testing, where you may want to run a function that usesrequest data without dispatching a full request.

SeeThe Request Context.

Use awith block to push the context, which will makerequest point at the request for the createdenvironment.

withapp.test_request_context(...):generate_report()

When using the shell, it may be easier to push and pop thecontext manually to avoid indentation.

ctx=app.test_request_context(...)ctx.push()...ctx.pop()

Takes the same arguments as Werkzeug’sEnvironBuilder, with some defaults fromthe application. See the linked Werkzeug docs for most of theavailable arguments. Flask-specific behavior is listed here.

Parameters:

path – URL path being requested.
base_url – Base URL where the app is being served, whichpath is relative to. If not given, built fromPREFERRED_URL_SCHEME,subdomain,SERVER_NAME, andAPPLICATION_ROOT.
subdomain – Subdomain name to append toSERVER_NAME.
url_scheme – Scheme to use instead ofPREFERRED_URL_SCHEME.
data – The request body, either as a string or a dict ofform keys and values.
json – If given, this is serialized as JSON and passed asdata. Also defaultscontent_type toapplication/json.
args (Any) – other positional arguments passed toEnvironBuilder.
kwargs (Any) – other keyword arguments passed toEnvironBuilder.

Return type:

RequestContext

wsgi_app(environ,start_response)¶

The actual WSGI application. This is not implemented in__call__() so that middlewares can be applied withoutlosing a reference to the app object. Instead of doing this:

app=MyMiddleware(app)

It’s a better idea to do this instead:

app.wsgi_app=MyMiddleware(app.wsgi_app)

Then you still have the original application object around andcan continue to call methods on it.

Changelog

Changed in version 0.7:Teardown events for the request and app contexts are calledeven if an unhandled error occurs. Other events may not becalled depending on when an error occurs during dispatch.SeeCallbacks and Errors.

Parameters:

environ (WSGIEnvironment) – A WSGI environment.
start_response (StartResponse) – A callable accepting a status code,a list of headers, and an optional exception context tostart the response.

Return type:

cabc.Iterable[bytes]

aborter_class¶: alias ofAborter

add_template_filter(f,name=None)¶

Parameters:

name (str |None) – the optional name of the filter, otherwise thefunction name will be used.
f (Callable[[...],Any])

Return type:

None

add_template_global(f,name=None)¶

Changelog

Added in version 0.10.

Parameters:

name (str |None) – the optional name of the global function, otherwise thefunction name will be used.
f (Callable[[...],Any])

Return type:

None

add_template_test(f,name=None)¶

Changelog

Added in version 0.10.

Parameters:

name (str |None) – the optional name of the test, otherwise thefunction name will be used.
f (Callable[[...],bool])

Return type:

None

add_url_rule(rule,endpoint=None,view_func=None,provide_automatic_options=None,**options)¶

Register a rule for routing incoming requests and buildingURLs. Theroute() decorator is a shortcut to call thiswith theview_func argument. These are equivalent:

@app.route("/")defindex():...

defindex():...app.add_url_rule("/",view_func=index)

SeeURL Route Registrations.

The endpoint name for the route defaults to the name of the viewfunction if theendpoint parameter isn’t passed. An errorwill be raised if a function has already been registered for theendpoint.

Themethods parameter defaults to["GET"].HEAD isalways added automatically, andOPTIONS is addedautomatically by default.

view_func does not necessarily need to be passed, but if therule should participate in routing an endpoint name must beassociated with a view function at some point with theendpoint() decorator.

app.add_url_rule("/",endpoint="index")@app.endpoint("index")defindex():...

Ifview_func has arequired_methods attribute, thosemethods are added to the passed and automatic methods. If ithas aprovide_automatic_methods attribute, it is used as thedefault if the parameter is not passed.

Parameters:

rule (str) – The URL rule string.
endpoint (str |None) – The endpoint name to associate with the ruleand view function. Used when routing and building URLs.Defaults toview_func.__name__.
view_func (ft.RouteCallable |None) – The view function to associate with theendpoint name.
provide_automatic_options (bool |None) – Add theOPTIONS method andrespond toOPTIONS requests automatically.
options (t.Any) – Extra options passed to theRule object.

Return type:

None

after_request(f)¶

The function is called with the response object, and must returna response object. This allows the functions to modify orreplace the response before it is sent.

If a function raises an exception, any remainingafter_request functions will not be called. Therefore, thisshould not be used for actions that must execute, such as toclose resources. Useteardown_request() for that.

This is available on both app and blueprint objects. When used on an app, thisexecutes after every request. When used on a blueprint, this executes afterevery request that the blueprint handles. To register with a blueprint andexecute after every request, useBlueprint.after_app_request().

Parameters:: f (T_after_request)
Return type:: T_after_request

app_ctx_globals_class¶: alias of_AppCtxGlobals

auto_find_instance_path()¶

Tries to locate the instance path if it was not provided to theconstructor of the application class. It will basically calculatethe path to a folder namedinstance next to your main file orthe package.

Changelog

Added in version 0.8.

Return type:: str

before_request(f)¶

For example, this can be used to open a database connection, orto load the logged in user from the session.

@app.before_requestdefload_user():if"user_id"insession:g.user=db.session.get(session["user_id"])

The function will be called without any arguments. If it returnsa non-None value, the value is handled as if it was thereturn value from the view, and further request handling isstopped.

This is available on both app and blueprint objects. When used on an app, thisexecutes before every request. When used on a blueprint, this executes beforeevery request that the blueprint handles. To register with a blueprint andexecute before every request, useBlueprint.before_app_request().

Parameters:: f (T_before_request)
Return type:: T_before_request

config_class¶: alias ofConfig

context_processor(f)¶

Registers a template context processor function. These functions run beforerendering a template. The keys of the returned dict are added as variablesavailable in the template.

This is available on both app and blueprint objects. When used on an app, thisis called for every rendered template. When used on a blueprint, this is calledfor templates rendered from the blueprint’s views. To register with a blueprintand affect every template, useBlueprint.app_context_processor().

Parameters:: f (T_template_context_processor)
Return type:: T_template_context_processor

create_global_jinja_loader()¶

Creates the loader for the Jinja environment. Can be used tooverride just the loader and keeping the rest unchanged. It’sdiscouraged to override this function. Instead one should overridethejinja_loader() function instead.

The global loader dispatches between the loaders of the applicationand the individual blueprints.

Changelog

Added in version 0.7.

Return type:: DispatchingJinjaLoader

propertydebug:bool¶

Whether debug mode is enabled. When usingflaskrun to start thedevelopment server, an interactive debugger will be shown for unhandledexceptions, and the server will be reloaded when code changes. This maps to theDEBUG config key. It may not behave as expected if set late.

Do not enable debug mode when deploying in production.

Default:False

delete(rule,**options)¶

Shortcut forroute() withmethods=["DELETE"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

endpoint(endpoint)¶

Decorate a view function to register it for the givenendpoint. Used if a rule is added without aview_func withadd_url_rule().

app.add_url_rule("/ex",endpoint="example")@app.endpoint("example")defexample():...

Parameters:: endpoint (str) – The endpoint name to associate with the viewfunction.
Return type:: Callable[[F],F]

errorhandler(code_or_exception)¶

A decorator that is used to register a function given anerror code. Example:

@app.errorhandler(404)defpage_not_found(error):return'This page does not exist',404

You can also register handlers for arbitrary exceptions:

@app.errorhandler(DatabaseError)defspecial_exception_handler(error):return'Database connection failed',500

This is available on both app and blueprint objects. When used on an app, thiscan handle errors from every request. When used on a blueprint, this can handleerrors from requests that the blueprint handles. To register with a blueprintand affect every request, useBlueprint.app_errorhandler().

Changelog

Added in version 0.7:Useregister_error_handler() instead of modifyingerror_handler_spec directly, for application wide errorhandlers.

Added in version 0.7:One can now additionally also register custom exception typesthat do not necessarily have to be a subclass of theHTTPException class.

Parameters:: code_or_exception (type[Exception]|int) – the code as integer for the handler, oran arbitrary exception
Return type:: Callable[[T_error_handler],T_error_handler]

get(rule,**options)¶

Shortcut forroute() withmethods=["GET"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

handle_url_build_error(error,endpoint,values)¶

Called byurl_for() if aBuildError was raised. If this returnsa value, it will be returned byurl_for, otherwise the errorwill be re-raised.

Each function inurl_build_error_handlers is called witherror,endpoint andvalues. If a function returnsNone or raises aBuildError, it is skipped. Otherwise,its return value is returned byurl_for.

Parameters:

error (BuildError) – The activeBuildError being handled.
endpoint (str) – The endpoint being built.
values (dict[str,Any]) – The keyword arguments passed tourl_for.

Return type:

propertyhas_static_folder:bool¶: True ifstatic_folder is set.
Changelog
Added in version 0.5.

inject_url_defaults(endpoint,values)¶

Injects the URL defaults for the given endpoint directly intothe values dictionary passed. This is used internally andautomatically called on URL building.

Changelog

Added in version 0.7.

Parameters:

endpoint (str)
values (dict[str,Any])

Return type:

None

iter_blueprints()¶

Iterates over all blueprints by the order they were registered.

Changelog

Added in version 0.11.

Return type:: t.ValuesView[Blueprint]

propertyjinja_env:Environment¶

The Jinja environment used to load templates.

The environment is created the first time this property isaccessed. Changingjinja_options after that will have noeffect.

jinja_environment¶: alias ofEnvironment

propertyjinja_loader:BaseLoader|None¶: The Jinja loader for this object’s templates. By default thisis a classjinja2.loaders.FileSystemLoader totemplate_folder if it is set.
Changelog
Added in version 0.5.

jinja_options:dict[str,t.Any]={}¶: Options that are passed to the Jinja environment increate_jinja_environment(). Changing these options afterthe environment is created (accessingjinja_env) willhave no effect.
Changelog
Changed in version 1.1.0:This is adict instead of anImmutableDict to alloweasier configuration.

json_provider_class¶: alias ofDefaultJSONProvider

propertylogger:Logger¶

A standard PythonLogger for the app, withthe same name asname.

In debug mode, the logger’slevel willbe set toDEBUG.

If there are no handlers configured, a default handler will beadded. SeeLogging for more information.

Changelog

Changed in version 1.1.0:The logger takes the same name asname rather thanhard-coding"flask.app".

Changed in version 1.0.0:Behavior was simplified. The logger is always named"flask.app". The level is only set during configuration,it doesn’t checkapp.debug each time. Only one format isused, not different ones depending onapp.debug. Nohandlers are removed, and a handler is only added if nohandlers are already configured.

Added in version 0.3.

make_aborter()¶

Create the object to assign toaborter. That objectis called byflask.abort() to raise HTTP errors, and canbe called directly as well.

By default, this creates an instance ofaborter_class,which defaults towerkzeug.exceptions.Aborter.

Changelog

Added in version 2.2.

Return type:: Aborter

make_config(instance_relative=False)¶

Used to create the config attribute by the Flask constructor.Theinstance_relative parameter is passed in from the constructorof Flask (there namedinstance_relative_config) and indicates ifthe config should be relative to the instance path or the root pathof the application.

Changelog

Added in version 0.8.

Parameters:: instance_relative (bool)
Return type:: Config

propertyname:str¶: The name of the application. This is usually the import namewith the difference that it’s guessed from the run file if theimport name is main. This name is used as a display name whenFlask needs the name of the application. It can be set and overriddento change the value.
Changelog
Added in version 0.8.

patch(rule,**options)¶

Shortcut forroute() withmethods=["PATCH"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

permanent_session_lifetime¶

Atimedelta which is used to set the expirationdate of a permanent session. The default is 31 days which makes apermanent session survive for roughly one month.

This attribute can also be configured from the config with thePERMANENT_SESSION_LIFETIME configuration key. Defaults totimedelta(days=31)

post(rule,**options)¶

Shortcut forroute() withmethods=["POST"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

put(rule,**options)¶

Shortcut forroute() withmethods=["PUT"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

redirect(location,code=302)¶

Create a redirect response object.

This is called byflask.redirect(), and can be calleddirectly as well.

Parameters:

location (str) – The URL to redirect to.
code (int) – The status code for the redirect.

Return type:

BaseResponse

Changelog

Added in version 2.2:Moved fromflask.redirect, which calls this method.

register_blueprint(blueprint,**options)¶

Register aBlueprint on the application. Keywordarguments passed to this method will override the defaults set on theblueprint.

Calls the blueprint’sregister() method afterrecording the blueprint in the application’sblueprints.

Parameters:

blueprint (Blueprint) – The blueprint to register.
url_prefix – Blueprint routes will be prefixed with this.
subdomain – Blueprint routes will match on this subdomain.
url_defaults – Blueprint routes will use these default values forview arguments.
options (t.Any) – Additional keyword arguments are passed toBlueprintSetupState. They can beaccessed inrecord() callbacks.

Return type:

None

Changelog

Changed in version 2.0.1:Thename option can be used to change the (pre-dotted)name the blueprint is registered with. This allows the sameblueprint to be registered multiple times with unique namesforurl_for.

Added in version 0.7.

register_error_handler(code_or_exception,f)¶

Alternative error attach function to theerrorhandler()decorator that is more straightforward to use for non decoratorusage.

Changelog

Added in version 0.7.

Parameters:

code_or_exception (type[Exception]|int)
f (ft.ErrorHandlerCallable)

Return type:

None

route(rule,**options)¶

Decorate a view function to register it with the given URLrule and options. Callsadd_url_rule(), which has moredetails about the implementation.

@app.route("/")defindex():return"Hello, World!"

SeeURL Route Registrations.

The endpoint name for the route defaults to the name of the viewfunction if theendpoint parameter isn’t passed.

Themethods parameter defaults to["GET"].HEAD andOPTIONS are added automatically.

Parameters:

rule (str) – The URL rule string.
options (Any) – Extra options passed to theRule object.

Return type:

Callable[[T_route],T_route]

secret_key¶

If a secret key is set, cryptographic components can use this tosign cookies and other things. Set this to a complex random valuewhen you want to use the secure cookie for instance.

This attribute can also be configured from the config with theSECRET_KEY configuration key. Defaults toNone.

select_jinja_autoescape(filename)¶

ReturnsTrue if autoescaping should be active for the giventemplate name. If no template name is given, returnsTrue.

Changelog

Changed in version 2.2:Autoescaping is now enabled by default for.svg files.

Added in version 0.5.

Parameters:: filename (str)
Return type:: bool

shell_context_processor(f)¶

Registers a shell context processor function.

Changelog

Added in version 0.11.

Parameters:: f (T_shell_context_processor)
Return type:: T_shell_context_processor

should_ignore_error(error)¶

This is called to figure out if an error should be ignoredor not as far as the teardown system is concerned. If thisfunction returnsTrue then the teardown handlers will not bepassed the error.

Changelog

Added in version 0.10.

Parameters:: error (BaseException |None)
Return type:: bool

propertystatic_folder:str|None¶: The absolute path to the configured static folder.Noneif no static folder is set.

propertystatic_url_path:str|None¶

The URL prefix that the static route will be accessible from.

If it was not configured during init, it is derived fromstatic_folder.

teardown_appcontext(f)¶

Registers a function to be called when the applicationcontext is popped. The application context is typically poppedafter the request context for each request, at the end of CLIcommands, or after a manually pushed context ends.

withapp.app_context():...

When thewith block exits (orctx.pop() is called), theteardown functions are called just before the app context ismade inactive. Since a request context typically also manages anapplication context it would also be called when you pop arequest context.

When a teardown function was called because of an unhandledexception it will be passed an error object. If anerrorhandler() is registered, it will handle the exceptionand the teardown will not receive it.

Teardown functions must avoid raising exceptions. If theyexecute code that might fail they must surround that code with atry/except block and log any errors.

The return values of teardown functions are ignored.

Changelog

Added in version 0.9.

Parameters:: f (T_teardown)
Return type:: T_teardown

teardown_request(f)¶

Register a function to be called when the request context ispopped. Typically this happens at the end of each request, butcontexts may be pushed manually as well during testing.

withapp.test_request_context():...

When thewith block exits (orctx.pop() is called), theteardown functions are called just before the request context ismade inactive.

Teardown functions must avoid raising exceptions. If theyexecute code that might fail they must surround that code with atry/except block and log any errors.

The return values of teardown functions are ignored.

Parameters:: f (T_teardown)
Return type:: T_teardown

template_filter(name=None)¶

A decorator that is used to register custom template filter.You can specify a name for the filter, otherwise the functionname will be used. Example:

@app.template_filter()defreverse(s):returns[::-1]

Parameters:: name (str |None) – the optional name of the filter, otherwise thefunction name will be used.
Return type:: Callable[[T_template_filter],T_template_filter]

template_global(name=None)¶

A decorator that is used to register a custom template global function.You can specify a name for the global function, otherwise the functionname will be used. Example:

@app.template_global()defdouble(n):return2*n

Changelog

Added in version 0.10.

Parameters:: name (str |None) – the optional name of the global function, otherwise thefunction name will be used.
Return type:: Callable[[T_template_global],T_template_global]

template_test(name=None)¶

A decorator that is used to register custom template test.You can specify a name for the test, otherwise the functionname will be used. Example:

@app.template_test()defis_prime(n):ifn==2:returnTrueforiinrange(2,int(math.ceil(math.sqrt(n)))+1):ifn%i==0:returnFalsereturnTrue

Changelog

Added in version 0.10.

Parameters:: name (str |None) – the optional name of the test, otherwise thefunction name will be used.
Return type:: Callable[[T_template_test],T_template_test]

test_cli_runner_class:type[FlaskCliRunner]|None=None¶: TheCliRunner subclass, by defaultFlaskCliRunner that is used bytest_cli_runner(). Its__init__ method should take aFlask app object as the first argument.
Changelog
Added in version 1.0.

test_client_class:type[FlaskClient]|None=None¶: Thetest_client() method creates an instance of this testclient class. Defaults toFlaskClient.
Changelog
Added in version 0.7.

testing¶

The testing flag. Set this toTrue to enable the test mode ofFlask extensions (and in the future probably also Flask itself).For example this might activate test helpers that have anadditional runtime cost which should not be enabled by default.

If this is enabled and PROPAGATE_EXCEPTIONS is not changed from thedefault it’s implicitly enabled.

This attribute can also be configured from the config with theTESTING configuration key. Defaults toFalse.

trap_http_exception(e)¶

Checks if an HTTP exception should be trapped or not. By defaultthis will returnFalse for all exceptions except for a bad requestkey error ifTRAP_BAD_REQUEST_ERRORS is set toTrue. Italso returnsTrue ifTRAP_HTTP_EXCEPTIONS is set toTrue.

This is called for all HTTP exceptions raised by a view function.If it returnsTrue for any exception the error handler for thisexception is not called and it shows up as regular exception in thetraceback. This is helpful for debugging implicitly raised HTTPexceptions.

Changelog

Changed in version 1.0:Bad request errors are not trapped by default in debug mode.

Added in version 0.8.

Parameters:: e (Exception)
Return type:: bool

url_defaults(f)¶

Callback function for URL defaults for all view functions of theapplication. It’s called with the endpoint and values and shouldupdate the values passed in place.

This is available on both app and blueprint objects. When used on an app, thisis called for every request. When used on a blueprint, this is called forrequests that the blueprint handles. To register with a blueprint and affectevery request, useBlueprint.app_url_defaults().

Parameters:: f (T_url_defaults)
Return type:: T_url_defaults

url_map_class¶: alias ofMap

url_rule_class¶: alias ofRule

url_value_preprocessor(f)¶

Register a URL value preprocessor function for all viewfunctions in the application. These functions will be called before thebefore_request() functions.

The function can modify the values captured from the matched url beforethey are passed to the view. For example, this can be used to pop acommon language code value and place it ing rather than pass it toevery view.

The function is passed the endpoint name and values dict. The returnvalue is ignored.

Parameters:: f (T_url_value_preprocessor)
Return type:: T_url_value_preprocessor

instance_path¶: Holds the path to the instance folder.
Changelog
Added in version 0.8.

config¶: The configuration dictionary asConfig. This behavesexactly like a regular dictionary but supports additional methodsto load a config from files.

aborter¶: An instance ofaborter_class created bymake_aborter(). This is called byflask.abort()to raise HTTP errors, and can be called directly as well.
Changelog
Added in version 2.2:Moved fromflask.abort, which calls this object.

json:JSONProvider¶

Provides access to JSON methods. Functions inflask.jsonwill call methods on this provider when the application contextis active. Used for handling JSON requests and responses.

An instance ofjson_provider_class. Can be customized bychanging that attribute on a subclass, or by assigning to thisattribute afterwards.

The default,DefaultJSONProvider,uses Python’s built-injson library. A different providercan use a different JSON library.

Changelog

Added in version 2.2.

url_build_error_handlers:list[t.Callable[[Exception,str,dict[str,t.Any]],str]]¶: A list of functions that are called byhandle_url_build_error() whenurl_for() raises aBuildError. Each function is calledwitherror,endpoint andvalues. If a functionreturnsNone or raises aBuildError, it is skipped.Otherwise, its return value is returned byurl_for.
Changelog
Added in version 0.9.

teardown_appcontext_funcs:list[ft.TeardownCallable]¶: A list of functions that are called when the application contextis destroyed. Since the application context is also torn downif the request ends this is the place to store code that disconnectsfrom databases.
Changelog
Added in version 0.9.

shell_context_processors:list[ft.ShellContextProcessorCallable]¶: A list of shell context processor functions that should be runwhen a shell context is created.
Changelog
Added in version 0.11.

blueprints:dict[str,Blueprint]¶: Maps registered blueprint names to blueprint objects. Thedict retains the order the blueprints were registered in.Blueprints can be registered multiple times, this dict doesnot track how often they were attached.
Changelog
Added in version 0.7.

extensions:dict[str,t.Any]¶

a place where extensions can store application specific state. Forexample this is where an extension could store database engines andsimilar things.

The key must match the name of the extension module. For example incase of a “Flask-Foo” extension inflask_foo, the key would be'foo'.

Changelog

Added in version 0.7.

url_map¶

TheMap for this instance. You can usethis to change the routing converters after the class was createdbut before any routes are connected. Example:

fromwerkzeug.routingimportBaseConverterclassListConverter(BaseConverter):defto_python(self,value):returnvalue.split(',')defto_url(self,values):return','.join(super(ListConverter,self).to_url(value)forvalueinvalues)app=Flask(__name__)app.url_map.converters['list']=ListConverter

import_name¶: The name of the package or module that this object belongsto. Do not change this once it is set by the constructor.

template_folder¶: The path to the templates folder, relative toroot_path, to add to the template loader.None iftemplates should not be added.

root_path¶: Absolute path to the package on the filesystem. Used to lookup resources contained in the package.

view_functions:dict[str,ft.RouteCallable]¶

A dictionary mapping endpoint names to view functions.

To register a view function, use theroute() decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

error_handler_spec:dict[ft.AppOrBlueprintKey,dict[int|None,dict[type[Exception],ft.ErrorHandlerCallable]]]¶

A data structure of registered error handlers, in the format{scope:{code:{class:handler}}}. Thescope key isthe name of a blueprint the handlers are active for, orNone for all requests. Thecode key is the HTTPstatus code forHTTPException, orNone forother exceptions. The innermost dictionary maps exceptionclasses to handler functions.

To register an error handler, use theerrorhandler()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

before_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.BeforeRequestCallable]]¶

A data structure of functions to call at the beginning ofeach request, in the format{scope:[functions]}. Thescope key is the name of a blueprint the functions areactive for, orNone for all requests.

To register a function, use thebefore_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

after_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.AfterRequestCallable[t.Any]]]¶

A data structure of functions to call at the end of eachrequest, in the format{scope:[functions]}. Thescope key is the name of a blueprint the functions areactive for, orNone for all requests.

To register a function, use theafter_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

teardown_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.TeardownCallable]]¶

A data structure of functions to call at the end of eachrequest even if an exception is raised, in the format{scope:[functions]}. Thescope key is the name of ablueprint the functions are active for, orNone for allrequests.

To register a function, use theteardown_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

template_context_processors:dict[ft.AppOrBlueprintKey,list[ft.TemplateContextProcessorCallable]]¶

A data structure of functions to call to pass extra contextvalues when rendering templates, in the format{scope:[functions]}. Thescope key is the name of ablueprint the functions are active for, orNone for allrequests.

To register a function, use thecontext_processor()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

url_value_preprocessors:dict[ft.AppOrBlueprintKey,list[ft.URLValuePreprocessorCallable]]¶

A data structure of functions to call to modify the keywordarguments passed to the view function, in the format{scope:[functions]}. Thescope key is the name of ablueprint the functions are active for, orNone for allrequests.

To register a function, use theurl_value_preprocessor() decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

url_default_functions:dict[ft.AppOrBlueprintKey,list[ft.URLDefaultCallable]]¶

A data structure of functions to call to modify the keywordarguments when generating URLs, in the format{scope:[functions]}. Thescope key is the name of ablueprint the functions are active for, orNone for allrequests.

To register a function, use theurl_defaults()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

Blueprint Objects¶

classflask.Blueprint(name,import_name,static_folder=None,static_url_path=None,template_folder=None,url_prefix=None,subdomain=None,url_defaults=None,root_path=None,cli_group=_sentinel)¶

Parameters:

name (str)
import_name (str)
static_folder (str |os.PathLike[str]|None)
static_url_path (str |None)
template_folder (str |os.PathLike[str]|None)
url_prefix (str |None)
subdomain (str |None)
url_defaults (dict[str,t.Any]|None)
root_path (str |None)
cli_group (str |None)

cli:Group¶: The Click command group for registering CLI commands for thisobject. The commands are available from theflask commandonce the application has been discovered and blueprints havebeen registered.

get_send_file_max_age(filename)¶

Used bysend_file() to determine themax_age cachevalue for a given file path if it wasn’t passed.

Note this is a duplicate of the same method in the Flaskclass.

Changelog

Changed in version 2.0:The default configuration isNone instead of 12 hours.

Added in version 0.9.

Parameters:: filename (str |None)
Return type:: int | None

send_static_file(filename)¶

The view function used to serve files fromstatic_folder. A route is automatically registered forthis view atstatic_url_path ifstatic_folder isset.

Note this is a duplicate of the same method in the Flaskclass.

Changelog

Added in version 0.5.

Parameters:: filename (str)
Return type:: Response

open_resource(resource,mode='rb',encoding='utf-8')¶

Open a resource file relative toroot_path for reading. Theblueprint-relative equivalent of the app’sopen_resource()method.

Parameters:

resource (str) – Path to the resource relative toroot_path.
mode (str) – Open the file in this mode. Only reading is supported,valid values are"r" (or"rt") and"rb".
encoding (str |None) – Open the file with this encoding when opening in textmode. This is ignored when opening in binary mode.

Return type:

Changed in version 3.1:Added theencoding parameter.

add_app_template_filter(f,name=None)¶

Register a template filter, available in any template rendered by theapplication. Works like theapp_template_filter() decorator. Equivalent toFlask.add_template_filter().

Parameters:

name (str |None) – the optional name of the filter, otherwise thefunction name will be used.
f (Callable[[...],Any])

Return type:

None

add_app_template_global(f,name=None)¶

Register a template global, available in any template rendered by theapplication. Works like theapp_template_global() decorator. Equivalent toFlask.add_template_global().

Changelog

Added in version 0.10.

Parameters:

name (str |None) – the optional name of the global, otherwise thefunction name will be used.
f (Callable[[...],Any])

Return type:

None

add_app_template_test(f,name=None)¶

Register a template test, available in any template rendered by theapplication. Works like theapp_template_test() decorator. Equivalent toFlask.add_template_test().

Changelog

Added in version 0.10.

Parameters:

name (str |None) – the optional name of the test, otherwise thefunction name will be used.
f (Callable[[...],bool])

Return type:

None

add_url_rule(rule,endpoint=None,view_func=None,provide_automatic_options=None,**options)¶

The URL rule is prefixed with the blueprint’s URL prefix. The endpoint name,used withurl_for(), is prefixed with the blueprint’s name.

Parameters:

rule (str)
endpoint (str |None)
view_func (ft.RouteCallable |None)
provide_automatic_options (bool |None)
options (t.Any)

Return type:

None

after_app_request(f)¶

Likeafter_request(), but after every request, not only those handledby the blueprint. Equivalent toFlask.after_request().

Parameters:: f (T_after_request)
Return type:: T_after_request

after_request(f)¶

The function is called with the response object, and must returna response object. This allows the functions to modify orreplace the response before it is sent.

Parameters:: f (T_after_request)
Return type:: T_after_request

app_context_processor(f)¶

Likecontext_processor(), but for templates rendered by every view, notonly by the blueprint. Equivalent toFlask.context_processor().

Parameters:: f (T_template_context_processor)
Return type:: T_template_context_processor

app_errorhandler(code)¶

Likeerrorhandler(), but for every request, not only those handled bythe blueprint. Equivalent toFlask.errorhandler().

Parameters:: code (type[Exception]|int)
Return type:: Callable[[T_error_handler],T_error_handler]

app_template_filter(name=None)¶

Register a template filter, available in any template rendered by theapplication. Equivalent toFlask.template_filter().

Parameters:: name (str |None) – the optional name of the filter, otherwise thefunction name will be used.
Return type:: Callable[[T_template_filter],T_template_filter]

app_template_global(name=None)¶

Register a template global, available in any template rendered by theapplication. Equivalent toFlask.template_global().

Changelog

Added in version 0.10.

Parameters:: name (str |None) – the optional name of the global, otherwise thefunction name will be used.
Return type:: Callable[[T_template_global],T_template_global]

app_template_test(name=None)¶

Changelog

Added in version 0.10.

Parameters:: name (str |None) – the optional name of the test, otherwise thefunction name will be used.
Return type:: Callable[[T_template_test],T_template_test]

app_url_defaults(f)¶

Likeurl_defaults(), but for every request, not only those handled bythe blueprint. Equivalent toFlask.url_defaults().

Parameters:: f (T_url_defaults)
Return type:: T_url_defaults

app_url_value_preprocessor(f)¶

Likeurl_value_preprocessor(), but for every request, not only thosehandled by the blueprint. Equivalent toFlask.url_value_preprocessor().

Parameters:: f (T_url_value_preprocessor)
Return type:: T_url_value_preprocessor

before_app_request(f)¶

Likebefore_request(), but before every request, not only those handledby the blueprint. Equivalent toFlask.before_request().

Parameters:: f (T_before_request)
Return type:: T_before_request

before_request(f)¶

For example, this can be used to open a database connection, orto load the logged in user from the session.

@app.before_requestdefload_user():if"user_id"insession:g.user=db.session.get(session["user_id"])

The function will be called without any arguments. If it returnsa non-None value, the value is handled as if it was thereturn value from the view, and further request handling isstopped.

Parameters:: f (T_before_request)
Return type:: T_before_request

context_processor(f)¶

Registers a template context processor function. These functions run beforerendering a template. The keys of the returned dict are added as variablesavailable in the template.

Parameters:: f (T_template_context_processor)
Return type:: T_template_context_processor

delete(rule,**options)¶

Shortcut forroute() withmethods=["DELETE"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

endpoint(endpoint)¶

Decorate a view function to register it for the givenendpoint. Used if a rule is added without aview_func withadd_url_rule().

app.add_url_rule("/ex",endpoint="example")@app.endpoint("example")defexample():...

Parameters:: endpoint (str) – The endpoint name to associate with the viewfunction.
Return type:: Callable[[F],F]

errorhandler(code_or_exception)¶

A decorator that is used to register a function given anerror code. Example:

@app.errorhandler(404)defpage_not_found(error):return'This page does not exist',404

You can also register handlers for arbitrary exceptions:

@app.errorhandler(DatabaseError)defspecial_exception_handler(error):return'Database connection failed',500

Changelog

Added in version 0.7:Useregister_error_handler() instead of modifyingerror_handler_spec directly, for application wide errorhandlers.

Added in version 0.7:One can now additionally also register custom exception typesthat do not necessarily have to be a subclass of theHTTPException class.

Parameters:: code_or_exception (type[Exception]|int) – the code as integer for the handler, oran arbitrary exception
Return type:: Callable[[T_error_handler],T_error_handler]

get(rule,**options)¶

Shortcut forroute() withmethods=["GET"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

propertyhas_static_folder:bool¶: True ifstatic_folder is set.
Changelog
Added in version 0.5.

propertyjinja_loader:BaseLoader|None¶: The Jinja loader for this object’s templates. By default thisis a classjinja2.loaders.FileSystemLoader totemplate_folder if it is set.
Changelog
Added in version 0.5.

make_setup_state(app,options,first_registration=False)¶

Creates an instance ofBlueprintSetupState()object that is later passed to the register callback functions.Subclasses can override this to return a subclass of the setup state.

Parameters:

app (App)
options (dict[str,t.Any])
first_registration (bool)

Return type:

BlueprintSetupState

patch(rule,**options)¶

Shortcut forroute() withmethods=["PATCH"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

post(rule,**options)¶

Shortcut forroute() withmethods=["POST"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

put(rule,**options)¶

Shortcut forroute() withmethods=["PUT"].

Changelog

Added in version 2.0.

Parameters:

rule (str)
options (Any)

Return type:

Callable[[T_route],T_route]

record(func)¶

Registers a function that is called when the blueprint isregistered on the application. This function is called with thestate as argument as returned by themake_setup_state()method.

Parameters:: func (Callable[[BlueprintSetupState],None])
Return type:: None

record_once(func)¶

Works likerecord() but wraps the function in anotherfunction that will ensure the function is only called once. If theblueprint is registered a second time on the application, thefunction passed is not called.

Parameters:: func (Callable[[BlueprintSetupState],None])
Return type:: None

register(app,options)¶

Called byFlask.register_blueprint() to register allviews and callbacks registered on the blueprint with theapplication. Creates aBlueprintSetupState and callseachrecord() callback with it.

Parameters:

app (App) – The application this blueprint is being registeredwith.
options (dict[str,t.Any]) – Keyword arguments forwarded fromregister_blueprint().

Return type:

None

Changelog

Changed in version 2.3:Nested blueprints now correctly apply subdomains.

Changed in version 2.1:Registering the same blueprint with the same name multipletimes is an error.

Changed in version 2.0.1:Nested blueprints are registered with their dotted name.This allows different blueprints with the same name to benested at different locations.

register_blueprint(blueprint,**options)¶

Register aBlueprint on this blueprint. Keywordarguments passed to this method will override the defaults seton the blueprint.

Changelog

Added in version 2.0.

Parameters:

blueprint (Blueprint)
options (Any)

Return type:

None

register_error_handler(code_or_exception,f)¶

Alternative error attach function to theerrorhandler()decorator that is more straightforward to use for non decoratorusage.

Changelog

Added in version 0.7.

Parameters:

code_or_exception (type[Exception]|int)
f (ft.ErrorHandlerCallable)

Return type:

None

route(rule,**options)¶

Decorate a view function to register it with the given URLrule and options. Callsadd_url_rule(), which has moredetails about the implementation.

@app.route("/")defindex():return"Hello, World!"

SeeURL Route Registrations.

The endpoint name for the route defaults to the name of the viewfunction if theendpoint parameter isn’t passed.

Themethods parameter defaults to["GET"].HEAD andOPTIONS are added automatically.

Parameters:

rule (str) – The URL rule string.
options (Any) – Extra options passed to theRule object.

Return type:

Callable[[T_route],T_route]

propertystatic_folder:str|None¶: The absolute path to the configured static folder.Noneif no static folder is set.

propertystatic_url_path:str|None¶

The URL prefix that the static route will be accessible from.

If it was not configured during init, it is derived fromstatic_folder.

teardown_app_request(f)¶

Liketeardown_request(), but after every request, not only thosehandled by the blueprint. Equivalent toFlask.teardown_request().

Parameters:: f (T_teardown)
Return type:: T_teardown

teardown_request(f)¶

Register a function to be called when the request context ispopped. Typically this happens at the end of each request, butcontexts may be pushed manually as well during testing.

withapp.test_request_context():...

When thewith block exits (orctx.pop() is called), theteardown functions are called just before the request context ismade inactive.

Teardown functions must avoid raising exceptions. If theyexecute code that might fail they must surround that code with atry/except block and log any errors.

The return values of teardown functions are ignored.

Parameters:: f (T_teardown)
Return type:: T_teardown

url_defaults(f)¶

Callback function for URL defaults for all view functions of theapplication. It’s called with the endpoint and values and shouldupdate the values passed in place.

Parameters:: f (T_url_defaults)
Return type:: T_url_defaults

url_value_preprocessor(f)¶

Register a URL value preprocessor function for all viewfunctions in the application. These functions will be called before thebefore_request() functions.

The function is passed the endpoint name and values dict. The returnvalue is ignored.

Parameters:: f (T_url_value_preprocessor)
Return type:: T_url_value_preprocessor

import_name¶: The name of the package or module that this object belongsto. Do not change this once it is set by the constructor.

template_folder¶: The path to the templates folder, relative toroot_path, to add to the template loader.None iftemplates should not be added.

root_path¶: Absolute path to the package on the filesystem. Used to lookup resources contained in the package.

view_functions:dict[str,ft.RouteCallable]¶

A dictionary mapping endpoint names to view functions.

To register a view function, use theroute() decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

error_handler_spec:dict[ft.AppOrBlueprintKey,dict[int|None,dict[type[Exception],ft.ErrorHandlerCallable]]]¶

To register an error handler, use theerrorhandler()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

before_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.BeforeRequestCallable]]¶

To register a function, use thebefore_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

after_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.AfterRequestCallable[t.Any]]]¶

A data structure of functions to call at the end of eachrequest, in the format{scope:[functions]}. Thescope key is the name of a blueprint the functions areactive for, orNone for all requests.

To register a function, use theafter_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

teardown_request_funcs:dict[ft.AppOrBlueprintKey,list[ft.TeardownCallable]]¶

To register a function, use theteardown_request()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

template_context_processors:dict[ft.AppOrBlueprintKey,list[ft.TemplateContextProcessorCallable]]¶

To register a function, use thecontext_processor()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

url_value_preprocessors:dict[ft.AppOrBlueprintKey,list[ft.URLValuePreprocessorCallable]]¶

To register a function, use theurl_value_preprocessor() decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

url_default_functions:dict[ft.AppOrBlueprintKey,list[ft.URLDefaultCallable]]¶

To register a function, use theurl_defaults()decorator.

This data structure is internal. It should not be modifieddirectly and its format may change at any time.

Incoming Request Data¶

classflask.Request(environ,populate_request=True,shallow=False)¶

The request object used by default in Flask. Remembers thematched endpoint and view arguments.

It is what ends up asrequest. If you want to replacethe request object used you can subclass this and setrequest_class to your subclass.

The request object is aRequest subclass andprovides all of the attributes Werkzeug defines plus a few Flaskspecific ones.

Parameters:

environ (WSGIEnvironment)
populate_request (bool)
shallow (bool)

url_rule:Rule|None=None¶: The internal URL rule that matched the request. This can beuseful to inspect which methods are allowed for the URL froma before/after handler (request.url_rule.methods) etc.Though if the request’s method was invalid for the URL rule,the valid list is available inrouting_exception.valid_methodsinstead (an attribute of the Werkzeug exceptionMethodNotAllowed)because the request was never internally bound.
Changelog
Added in version 0.6.

view_args:dict[str,t.Any]|None=None¶: A dict of view arguments that matched the request. If an exceptionhappened when matching, this will beNone.

routing_exception:HTTPException|None=None¶: If matching the URL failed, this is the exception that will beraised / was raised as part of the request handling. This isusually aNotFound exception orsomething similar.

propertymax_content_length:int|None¶

The maximum number of bytes that will be read during this request. Ifthis limit is exceeded, a 413RequestEntityTooLargeerror is raised. If it is set toNone, no limit is enforced at theFlask application level. However, if it isNone and the request hasnoContent-Length header and the WSGI server does not indicate thatit terminates the stream, then no data is read to avoid an infinitestream.

Each request defaults to theMAX_CONTENT_LENGTH config, whichdefaults toNone. It can be set on a specificrequest to applythe limit to that specific view. This should be set appropriately basedon an application’s or view’s specific needs.

Changed in version 3.1:This can be set per-request.

Changelog

Changed in version 0.6:This is configurable through Flask config.

propertymax_form_memory_size:int|None¶

The maximum size in bytes any non-file form field may be in amultipart/form-data body. If this limit is exceeded, a 413RequestEntityTooLarge error is raised. If itis set toNone, no limit is enforced at the Flask application level.

Each request defaults to theMAX_FORM_MEMORY_SIZE config, whichdefaults to500_000. It can be set on a specificrequest toapply the limit to that specific view. This should be set appropriatelybased on an application’s or view’s specific needs.

Changed in version 3.1:This is configurable through Flask config.

propertymax_form_parts:int|None¶

The maximum number of fields that may be present in amultipart/form-data body. If this limit is exceeded, a 413RequestEntityTooLarge error is raised. If itis set toNone, no limit is enforced at the Flask application level.

Each request defaults to theMAX_FORM_PARTS config, whichdefaults to1_000. It can be set on a specificrequest to applythe limit to that specific view. This should be set appropriately basedon an application’s or view’s specific needs.

Changed in version 3.1:This is configurable through Flask config.

propertyendpoint:str|None¶

The endpoint that matched the request URL.

This will beNone if matching failed or has not beenperformed yet.

This in combination withview_args can be used toreconstruct the same URL or a modified URL.

propertyblueprint:str|None¶

The registered name of the current blueprint.

This will beNone if the endpoint is not part of ablueprint, or if URL matching failed or has not been performedyet.

This does not necessarily match the name the blueprint wascreated with. It may have been nested, or registered with adifferent name.

propertyblueprints:list[str]¶

The registered names of the current blueprint upwards throughparent blueprints.

This will be an empty list if there is no current blueprint, orif URL matching failed.

Changelog

Added in version 2.0.1.

on_json_loading_failed(e)¶

Called ifget_json() fails and isn’t silenced.

If this method returns a value, it is used as the return valueforget_json(). The default implementation raisesBadRequest.

Parameters:: e (ValueError |None) – If parsing failed, this is the exception. It will beNone if the content type wasn’tapplication/json.
Return type:: Any

Changelog

Changed in version 2.3:Raise a 415 error instead of 400.

propertyaccept_charsets:CharsetAccept¶: List of charsets this client supports asCharsetAccept object.

propertyaccept_encodings:Accept¶: List of encodings this client accepts. Encodings in a HTTP termare compression encodings such as gzip. For charsets have a look ataccept_charset.

propertyaccept_languages:LanguageAccept¶: List of languages this client accepts asLanguageAccept object.

propertyaccept_mimetypes:MIMEAccept¶: List of mimetypes this client supports asMIMEAccept object.

access_control_request_headers¶: Sent with a preflight request to indicate which headers will be sent with the cross origin request. Setaccess_control_allow_headers on the response to indicate which headers are allowed.

access_control_request_method¶: Sent with a preflight request to indicate which method will be used for the cross origin request. Setaccess_control_allow_methods on the response to indicate which methods are allowed.

propertyaccess_route:list[str]¶: If a forwarded header exists this is a list of all ip addressesfrom the client ip to the last proxy server.

classmethodapplication(f)¶

Decorate a function as responder that accepts the request asthe last argument. This works like theresponder()decorator but the function is passed the request object as thelast argument and the request object will be closedautomatically:

@Request.applicationdefmy_wsgi_app(request):returnResponse('Hello World!')

As of Werkzeug 0.14 HTTP exceptions are automatically caught andconverted to responses instead of failing.

Parameters:: f (t.Callable[[Request],WSGIApplication]) – the WSGI callable to decorate
Returns:: a new WSGI callable
Return type:: WSGIApplication

propertyargs:MultiDict[str,str]¶

The parsed URL parameters (the part in the URL after the questionmark).

By default anImmutableMultiDictis returned from this function. This can be changed by settingparameter_storage_class to a different type. This mightbe necessary if the order of the form data is important.

Changelog

Changed in version 2.3:Invalid bytes remain percent encoded.

propertyauthorization:Authorization|None¶: TheAuthorization header parsed into anAuthorization object.None if the header is not present.
Changelog
Changed in version 2.3:Authorization is no longer adict. Thetoken attributewas added for auth schemes that use a token instead of parameters.

propertybase_url:str¶: Likeurl but without the query string.

propertycache_control:RequestCacheControl¶: ARequestCacheControl objectfor the incoming cache control headers.

close()¶

Closes associated resources of this request object. Thiscloses all file handles explicitly. You can also use the requestobject in a with statement which will automatically close it.

Changelog

Added in version 0.9.

Return type:: None

content_encoding¶: The Content-Encoding entity-header field is used as amodifier to the media-type. When present, its value indicateswhat additional content codings have been applied to theentity-body, and thus what decoding mechanisms must be appliedin order to obtain the media-type referenced by the Content-Typeheader field.
Changelog
Added in version 0.9.

propertycontent_length:int|None¶: The Content-Length entity-header field indicates the size of theentity-body in bytes or, in the case of the HEAD method, the size ofthe entity-body that would have been sent had the request been aGET.

content_md5¶: The Content-MD5 entity-header field, as defined inRFC 1864, is an MD5 digest of the entity-body for the purpose ofproviding an end-to-end message integrity check (MIC) of theentity-body. (Note: a MIC is good for detecting accidentalmodification of the entity-body in transit, but is not proofagainst malicious attacks.)
Changelog
Added in version 0.9.

content_type¶: The Content-Type entity-header field indicates the mediatype of the entity-body sent to the recipient or, in the case ofthe HEAD method, the media type that would have been sent hadthe request been a GET.

propertycookies:ImmutableMultiDict[str,str]¶: Adict with the contents of all cookies transmitted withthe request.

propertydata:bytes¶

The raw data read fromstream. Will be empty if the requestrepresents form data.

To get the raw data even if it represents form data, useget_data().

date¶: The Date general-header field represents the date andtime at which the message was originated, having the samesemantics as orig-date in RFC 822.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

dict_storage_class¶: alias ofImmutableMultiDict

propertyfiles:ImmutableMultiDict[str,FileStorage]¶

MultiDict object containingall uploaded files. Each key infiles is the name from the<inputtype="file"name="">. Each value infiles is aWerkzeugFileStorage object.

It basically behaves like a standard file object you know from Python,with the difference that it also has asave() function that canstore the file on the filesystem.

Note thatfiles will only contain data if the request method wasPOST, PUT or PATCH and the<form> that posted to the request hadenctype="multipart/form-data". It will be empty otherwise.

See theMultiDict /FileStorage documentation formore details about the used data structure.

propertyform:ImmutableMultiDict[str,str]¶

The form parameters. By default anImmutableMultiDictis returned from this function. This can be changed by settingparameter_storage_class to a different type. This mightbe necessary if the order of the form data is important.

Please keep in mind that file uploads will not end up here, but insteadin thefiles attribute.

Changelog

Changed in version 0.9:Previous to Werkzeug 0.9 this would only contain form data for POSTand PUT requests.

form_data_parser_class¶: alias ofFormDataParser

classmethodfrom_values(*args,**kwargs)¶

Create a new request object based on the values provided. Ifenviron is given missing values are filled from there. This method isuseful for small scripts when you need to simulate a request from an URL.Do not use this method for unittesting, there is a full featured clientobject (Client) that allows to create multipart requests,support for cookies etc.

This accepts the same options as theEnvironBuilder.

Changelog

Changed in version 0.5:This method now accepts the same arguments asEnvironBuilder. Because of this theenviron parameter is now calledenviron_overrides.

Returns:

request object

Parameters:

args (Any)
kwargs (Any)

Return type:

Request

propertyfull_path:str¶: Requested path, including the query string.

get_data(cache=True,as_text=False,parse_form_data=False)¶

This reads the buffered incoming data from the client into onebytes object. By default this is cached but that behavior can bechanged by settingcache toFalse.

Usually it’s a bad idea to call this method without checking thecontent length first as a client could send dozens of megabytes or moreto cause memory problems on the server.

Note that if the form data was already parsed this method will notreturn anything as form data parsing does not cache the data likethis method does. To implicitly invoke form data parsing functionsetparse_form_data toTrue. When this is done the return valueof this method will be an empty string if the form parser handlesthe data. This generally is not necessary as if the whole data iscached (which is the default) the form parser will used the cacheddata to parse the form data. Please be generally aware of checkingthe content length first in any case before calling this methodto avoid exhausting server memory.

Ifas_text is set toTrue the return value will be a decodedstring.

Changelog

Added in version 0.9.

Parameters:

cache (bool)
as_text (bool)
parse_form_data (bool)

Return type:

bytes |str

get_json(force=False,silent=False,cache=True)¶

Parsedata as JSON.

If the mimetype does not indicate JSON(application/json, seeis_json), or parsingfails,on_json_loading_failed() is called andits return value is used as the return value. By default thisraises a 415 Unsupported Media Type resp.

Parameters:

force (bool) – Ignore the mimetype and always try to parse JSON.
silent (bool) – Silence mimetype and parsing errors, andreturnNone instead.
cache (bool) – Store the parsed JSON to return for subsequentcalls.

Return type:

Any | None

Changelog

Changed in version 2.3:Raise a 415 error instead of 400.

Changed in version 2.1:Raise a 400 error if the content type is incorrect.

propertyhost:str¶: The host name the request was made to, including the port ifit’s non-standard. Validated withtrusted_hosts.

propertyhost_url:str¶: The request URL scheme and host only.

propertyif_match:ETags¶

An object containing all the etags in theIf-Match header.

Return type:: ETags

propertyif_modified_since:datetime|None¶: The parsedIf-Modified-Since header as a datetime object.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

propertyif_none_match:ETags¶

An object containing all the etags in theIf-None-Match header.

Return type:: ETags

propertyif_range:IfRange¶: The parsedIf-Range header.
Changelog
Changed in version 2.0:IfRange.date is timezone-aware.
Added in version 0.7.

propertyif_unmodified_since:datetime|None¶: The parsedIf-Unmodified-Since header as a datetime object.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

input_stream¶

The raw WSGI input stream, without any safety checks.

This is dangerous to use. It does not guard against infinite streams or readingpastcontent_length ormax_content_length.

Usestream instead.

propertyis_json:bool¶: Check if the mimetype indicates JSON data, eitherapplication/json orapplication/*+json.

is_multiprocess¶: boolean that isTrue if the application is served by aWSGI server that spawns multiple processes.

is_multithread¶: boolean that isTrue if the application is served by amultithreaded WSGI server.

is_run_once¶: boolean that isTrue if the application will beexecuted only once in a process lifetime. This is the case forCGI for example, but it’s not guaranteed that the execution onlyhappens one time.

propertyis_secure:bool¶: True if the request was made with a secure protocol(HTTPS or WSS).

propertyjson:Any|None¶

The parsed JSON data ifmimetype indicates JSON(application/json, seeis_json).

Callsget_json() with default arguments.

If the request content type is notapplication/json, thiswill raise a 415 Unsupported Media Type error.

Changelog

Changed in version 2.3:Raise a 415 error instead of 400.

Changed in version 2.1:Raise a 400 error if the content type is incorrect.

list_storage_class¶: alias ofImmutableList

make_form_data_parser()¶

Creates the form data parser. Instantiates theform_data_parser_class with some parameters.

Changelog

Added in version 0.8.

Return type:: FormDataParser

max_forwards¶: The Max-Forwards request-header field provides amechanism with the TRACE and OPTIONS methods to limit the numberof proxies or gateways that can forward the request to the nextinbound server.

propertymimetype:str¶: Likecontent_type, but without parameters (eg, withoutcharset, type etc.) and always lowercase. For example if the contenttype istext/HTML;charset=utf-8 the mimetype would be'text/html'.

propertymimetype_params:dict[str,str]¶: The mimetype parameters as dict. For example if the contenttype istext/html;charset=utf-8 the params would be{'charset':'utf-8'}.

origin¶: The host that the request originated from. Setaccess_control_allow_origin on the response to indicate which origins are allowed.

parameter_storage_class¶: alias ofImmutableMultiDict

propertypragma:HeaderSet¶: The Pragma general-header field is used to includeimplementation-specific directives that might apply to any recipientalong the request/response chain. All pragma directives specifyoptional behavior from the viewpoint of the protocol; however, somesystems MAY require that behavior be consistent with the directives.

propertyrange:Range|None¶

The parsedRange header.

Changelog

Added in version 0.7.

Return type:: Range

referrer¶: The Referer[sic] request-header field allows the clientto specify, for the server’s benefit, the address (URI) of theresource from which the Request-URI was obtained (the“referrer”, although the header field is misspelled).

remote_user¶: If the server supports user authentication, and thescript is protected, this attribute contains the username theuser has authenticated as.

propertyroot_url:str¶: The request URL scheme, host, and root path. This is the rootthat the application is accessed from.

propertyscript_root:str¶: Alias forself.root_path.environ["SCRIPT_ROOT"]without a trailing slash.

propertystream:IO[bytes]¶

The WSGI input stream, with safety checks. This stream can only be consumedonce.

Useget_data() to get the full data as bytes or text. Thedataattribute will contain the full bytes only if they do not represent form data.Theform attribute will contain the parsed form data in that case.

Unlikeinput_stream, this stream guards against infinite streams orreading pastcontent_length ormax_content_length.

Ifmax_content_length is set, it can be enforced on streams ifwsgi.input_terminated is set. Otherwise, an empty stream is returned.

If the limit is reached before the underlying stream is exhausted (such as afile that is too large, or an infinite stream), the remaining contents of thestream cannot be read safely. Depending on how the server handles this, clientsmay show a “connection reset” failure instead of seeing the 413 response.

Changelog

Changed in version 2.3:Checkmax_content_length preemptively and while reading.

Changed in version 0.9:The stream is always set (but may be consumed) even if form parsing wasaccessed first.

trusted_hosts:list[str]|None=None¶

Valid host names when handling requests. By default all hosts aretrusted, which means that whatever the client says the host iswill be accepted.

BecauseHost andX-Forwarded-Host headers can be set toany value by a malicious client, it is recommended to either setthis property or implement similar validation in the proxy (ifthe application is being run behind one).

Changelog

Added in version 0.9.

propertyurl:str¶: The full request URL with the scheme, host, root path, path,and query string.

propertyurl_root:str¶: Alias forroot_url. The URL with scheme, host, androot path. For example,https://example.com/app/.

propertyuser_agent:UserAgent¶: The user agent. Useuser_agent.string to get the headervalue. Setuser_agent_class to a subclass ofUserAgent to provide parsing forthe other properties or other extended data.
Changelog
Changed in version 2.1:The built-in parser was removed. Setuser_agent_class to aUserAgentsubclass to parse data from the string.

user_agent_class¶: alias ofUserAgent

propertyvalues:CombinedMultiDict[str,str]¶

Awerkzeug.datastructures.CombinedMultiDict thatcombinesargs andform.

For GET requests, onlyargs are present, notform.

Changelog

Changed in version 2.0:For GET requests, onlyargs are present, notform.

propertywant_form_data_parsed:bool¶: True if the request method carries content. By defaultthis is true if aContent-Type is sent.
Changelog
Added in version 0.8.

environ:WSGIEnvironment¶: The WSGI environment containing HTTP headers and information fromthe WSGI server.

shallow:bool¶: Set when creating the request object. IfTrue, reading fromthe request body will cause aRuntimeException. Useful toprevent modifying the stream from middleware.

method¶: The method the request was made with, such asGET.

scheme¶: The URL scheme of the protocol the request used, such ashttps orwss.

server¶: The address of the server.(host,port),(path,None)for unix sockets, orNone if not known.

root_path¶: The prefix that the application is mounted under, without atrailing slash.path comes after this.

path¶: The path part of the URL afterroot_path. This is thepath used for routing within the application.

query_string¶: The part of the URL after the “?”. This is the raw value, useargs for the parsed values.

headers¶: The headers received with the request.

remote_addr¶: The address of the client sending the request.

flask.request¶

To access incoming request data, you can use the globalrequestobject. Flask parses incoming request data for you and gives youaccess to it through that global object. Internally Flask makessure that you always get the correct data for the active thread if youare in a multithreaded environment.

This is a proxy. SeeNotes On Proxies for more information.

The request object is an instance of aRequest.

Response Objects¶

classflask.Response(response=None,status=None,headers=None,mimetype=None,content_type=None,direct_passthrough=False)¶

The response object that is used by default in Flask. Works like theresponse object from Werkzeug but is set to have an HTML mimetype bydefault. Quite often you don’t have to create this object yourself becausemake_response() will take care of that for you.

If you want to replace the response object used you can subclass this andsetresponse_class to your subclass.

Changelog

Changed in version 1.0:JSON support is added to the response, like the request. This is usefulwhen testing to get the test client response data as JSON.

Changed in version 1.0:Addedmax_cookie_size.

Parameters:

response (Iterable[str]|Iterable[bytes])
status (int |str |HTTPStatus |None)
headers (Headers)
mimetype (str |None)
content_type (str |None)
direct_passthrough (bool)

default_mimetype:str|None='text/html'¶: the default mimetype if none is provided.

accept_ranges¶

TheAccept-Ranges header. Even though the name wouldindicate that multiple values are supported, it must be onestring token only.

The values'bytes' and'none' are common.

Changelog

Added in version 0.7.

propertyaccess_control_allow_credentials:bool¶: Whether credentials can be shared by the browser toJavaScript code. As part of the preflight request it indicateswhether credentials can be used on the cross origin request.

access_control_allow_headers¶: Which headers can be sent with the cross origin request.

access_control_allow_methods¶: Which methods can be used for the cross origin request.

access_control_allow_origin¶: The origin or ‘*’ for any origin that may make cross origin requests.

access_control_expose_headers¶: Which headers can be shared by the browser to JavaScript code.

access_control_max_age¶: The maximum age in seconds the access control settings can be cached for.

add_etag(overwrite=False,weak=False)¶

Add an etag for the current response if there is none yet.

Changelog

Changed in version 2.0:SHA-1 is used to generate the value. MD5 may not beavailable in some environments.

Parameters:

overwrite (bool)
weak (bool)

Return type:

None

age¶

The Age response-header field conveys the sender’sestimate of the amount of time since the response (or itsrevalidation) was generated at the origin server.

Age values are non-negative decimal integers, representing timein seconds.

propertyallow:HeaderSet¶: The Allow entity-header field lists the set of methodssupported by the resource identified by the Request-URI. Thepurpose of this field is strictly to inform the recipient ofvalid methods associated with the resource. An Allow headerfield MUST be present in a 405 (Method Not Allowed)response.

automatically_set_content_length=True¶: Should this response object automatically set the content-lengthheader if possible? This is true by default.
Changelog
Added in version 0.8.

propertycache_control:ResponseCacheControl¶: The Cache-Control general-header field is used to specifydirectives that MUST be obeyed by all caching mechanisms along therequest/response chain.

calculate_content_length()¶

Returns the content length if available orNone otherwise.

Return type:: int | None

call_on_close(func)¶

Adds a function to the internal list of functions that shouldbe called as part of closing down the response. Since 0.7 thisfunction also returns the function that was passed so that thiscan be used as a decorator.

Changelog

Added in version 0.6.

Parameters:: func (Callable[[],Any])
Return type:: Callable[[],Any]

close()¶

Close the wrapped response if possible. You can also use the objectin a with statement which will automatically close it.

Changelog

Added in version 0.9:Can now be used in a with statement.

Return type:: None

content_encoding¶: The Content-Encoding entity-header field is used as amodifier to the media-type. When present, its value indicateswhat additional content codings have been applied to theentity-body, and thus what decoding mechanisms must be appliedin order to obtain the media-type referenced by the Content-Typeheader field.

propertycontent_language:HeaderSet¶: The Content-Language entity-header field describes thenatural language(s) of the intended audience for the enclosedentity. Note that this might not be equivalent to all thelanguages used within the entity-body.

content_length¶: The Content-Length entity-header field indicates the sizeof the entity-body, in decimal number of OCTETs, sent to therecipient or, in the case of the HEAD method, the size of theentity-body that would have been sent had the request been aGET.

content_location¶: The Content-Location entity-header field MAY be used tosupply the resource location for the entity enclosed in themessage when that entity is accessible from a location separatefrom the requested resource’s URI.

content_md5¶: The Content-MD5 entity-header field, as defined inRFC 1864, is an MD5 digest of the entity-body for the purpose ofproviding an end-to-end message integrity check (MIC) of theentity-body. (Note: a MIC is good for detecting accidentalmodification of the entity-body in transit, but is not proofagainst malicious attacks.)

propertycontent_range:ContentRange¶: TheContent-Range header as aContentRange object. Availableeven if the header is not set.
Changelog
Added in version 0.7.

propertycontent_security_policy:ContentSecurityPolicy¶

TheContent-Security-Policy header as aContentSecurityPolicy object. Availableeven if the header is not set.

The Content-Security-Policy header adds an additional layer ofsecurity to help detect and mitigate certain types of attacks.

propertycontent_security_policy_report_only:ContentSecurityPolicy¶

TheContent-Security-policy-report-only header as aContentSecurityPolicy object. Availableeven if the header is not set.

The Content-Security-Policy-Report-Only header adds a csp policythat is not enforced but is reported thereby helping detectcertain types of attacks.

content_type¶: The Content-Type entity-header field indicates the mediatype of the entity-body sent to the recipient or, in the case ofthe HEAD method, the media type that would have been sent hadthe request been a GET.

cross_origin_embedder_policy¶: Prevents a document from loading any cross-origin resources that do notexplicitly grant the document permission. Values must be a member of thewerkzeug.http.COEP enum.

cross_origin_opener_policy¶: Allows control over sharing of browsing context group with cross-origindocuments. Values must be a member of thewerkzeug.http.COOP enum.

propertydata:bytes|str¶: A descriptor that callsget_data() andset_data().

date¶: The Date general-header field represents the date andtime at which the message was originated, having the samesemantics as orig-date in RFC 822.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

default_status=200¶: the default status if none is provided.

delete_cookie(key,path='/',domain=None,secure=False,httponly=False,samesite=None,partitioned=False)¶

Delete a cookie. Fails silently if key doesn’t exist.

Parameters:

key (str) – the key (name) of the cookie to be deleted.
path (str |None) – if the cookie that should be deleted was limited to apath, the path has to be defined here.
domain (str |None) – if the cookie that should be deleted was limited to adomain, that domain has to be defined here.
secure (bool) – IfTrue, the cookie will only be availablevia HTTPS.
httponly (bool) – Disallow JavaScript access to the cookie.
samesite (str |None) – Limit the scope of the cookie to only beattached to requests that are “same-site”.
partitioned (bool) – IfTrue, the cookie will be partitioned.

Return type:

None

expires¶: The Expires entity-header field gives the date/time afterwhich the response is considered stale. A stale cache entry maynot normally be returned by a cache.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

classmethodforce_type(response,environ=None)¶

Enforce that the WSGI response is a response object of the currenttype. Werkzeug will use theResponse internally in manysituations like the exceptions. If you callget_response() on anexception you will get back a regularResponse object, evenif you are using a custom subclass.

This method can enforce a given response type, and it will alsoconvert arbitrary WSGI callables into response objects if an environis provided:

# convert a Werkzeug response object into an instance of the# MyResponseClass subclass.response=MyResponseClass.force_type(response)# convert any WSGI application into a response objectresponse=MyResponseClass.force_type(response,environ)

This is especially useful if you want to post-process responses inthe main dispatcher and use functionality provided by your subclass.

Keep in mind that this will modify response objects in place ifpossible!

Parameters:

response (Response) – a response object or wsgi application.
environ (WSGIEnvironment |None) – a WSGI environment object.

Returns:

a response object.

Return type:

freeze()¶

Make the response object ready to be pickled. Does thefollowing:

Buffer the response into a list, ignoringimplicity_sequence_conversion anddirect_passthrough.
Set theContent-Length header.
Generate anETag header if one is not already set.

Changelog

Changed in version 2.1:Removed theno_etag parameter.

Changed in version 2.0:AnETag header is always added.

Changed in version 0.6:TheContent-Length header is set.

Return type:: None

classmethodfrom_app(app,environ,buffered=False)¶

Create a new response object from an application output. Thisworks best if you pass it an application that returns a generator allthe time. Sometimes applications may use thewrite() callablereturned by thestart_response function. This tries to resolve suchedge cases automatically. But if you don’t get the expected outputyou should setbuffered toTrue which enforces buffering.

Parameters:

app (WSGIApplication) – the WSGI application to execute.
environ (WSGIEnvironment) – the WSGI environment to execute against.
buffered (bool) – set toTrue to enforce buffering.

Returns:

a response object.

Return type:

get_app_iter(environ)¶

Returns the application iterator for the given environ. Dependingon the request method and the current status code the return valuemight be an empty response rather than the one from the response.

If the request method isHEAD or the status code is in a rangewhere the HTTP specification requires an empty response, an emptyiterable is returned.

Changelog

Added in version 0.6.

Parameters:: environ (WSGIEnvironment) – the WSGI environment of the request.
Returns:: a response iterable.
Return type:: t.Iterable[bytes]

get_data(as_text=False)¶

The string representation of the response body. Whenever you callthis property the response iterable is encoded and flattened. Thiscan lead to unwanted behavior if you stream big data.

This behavior can be disabled by settingimplicit_sequence_conversion toFalse.

Ifas_text is set toTrue the return value will be a decodedstring.

Changelog

Added in version 0.9.

Parameters:: as_text (bool)
Return type:: bytes |str

get_etag()¶

Return a tuple in the form(etag,is_weak). If there is noETag the return value is(None,None).

Return type:: tuple[str,bool] |tuple[None, None]

get_json(force=False,silent=False)¶

Parsedata as JSON. Useful during testing.

If the mimetype does not indicate JSON(application/json, seeis_json), thisreturnsNone.

UnlikeRequest.get_json(), the result is not cached.

Parameters:

force (bool) – Ignore the mimetype and always try to parse JSON.
silent (bool) – Silence parsing errors and returnNoneinstead.

Return type:

Any | None

get_wsgi_headers(environ)¶

This is automatically called right before the response is startedand returns headers modified for the given environment. It returns acopy of the headers from the response with some modifications appliedif necessary.

For example the location header (if present) is joined with the rootURL of the environment. Also the content length is automatically setto zero here for certain status codes.

Changelog

Changed in version 0.6:Previously that function was calledfix_headers and modifiedthe response object in place. Also since 0.6, IRIs in locationand content-location headers are handled properly.

Also starting with 0.6, Werkzeug will attempt to set the contentlength if it is able to figure it out on its own. This is thecase if all the strings in the response iterable are alreadyencoded and the iterable is buffered.

Parameters:: environ (WSGIEnvironment) – the WSGI environment of the request.
Returns:: returns a newHeadersobject.
Return type:: Headers

get_wsgi_response(environ)¶

Returns the final WSGI response as tuple. The first item inthe tuple is the application iterator, the second the status andthe third the list of headers. The response returned is createdspecially for the given environment. For example if the requestmethod in the WSGI environment is'HEAD' the response willbe empty and only the headers and status code will be present.

Changelog

Added in version 0.6.

Parameters:: environ (WSGIEnvironment) – the WSGI environment of the request.
Returns:: an(app_iter,status,headers) tuple.
Return type:: tuple[t.Iterable[bytes],str,list[tuple[str,str]]]

implicit_sequence_conversion=True¶: if set toFalse accessing properties on the response object willnot try to consume the response iterator and convert it into a list.
Changelog
Added in version 0.6.2:That attribute was previously calledimplicit_seqence_conversion.(Notice the typo). If you did use this feature, you have to adaptyour code to the name change.

propertyis_json:bool¶: Check if the mimetype indicates JSON data, eitherapplication/json orapplication/*+json.

propertyis_sequence:bool¶: If the iterator is buffered, this property will beTrue. Aresponse object will consider an iterator to be buffered if theresponse attribute is a list or tuple.
Changelog
Added in version 0.6.

propertyis_streamed:bool¶

If the response is streamed (the response is not an iterable witha length information) this property isTrue. In this case streamedmeans that there is no information about the number of iterations.This is usuallyTrue if a generator is passed to the response object.

This is useful for checking before applying some sort of postfiltering that should not take place for streamed responses.

iter_encoded()¶

Iter the response encoded with the encoding of the response.If the response object is invoked as WSGI application the returnvalue of this method is used as application iterator unlessdirect_passthrough was activated.

Return type:: Iterator[bytes]

propertyjson:Any|None¶

The parsed JSON data ifmimetype indicates JSON(application/json, seeis_json).

Callsget_json() with default arguments.

last_modified¶: The Last-Modified entity-header field indicates the dateand time at which the origin server believes the variant waslast modified.
Changelog
Changed in version 2.0:The datetime object is timezone-aware.

location¶: The Location response-header field is used to redirectthe recipient to a location other than the Request-URI forcompletion of the request or identification of a newresource.

make_conditional(request_or_environ,accept_ranges=False,complete_length=None)¶

Make the response conditional to the request. This method worksbest if an etag was defined for the response already. Theadd_etagmethod can be used to do that. If called without etag just the dateheader is set.

This does nothing if the request method in the request or environ isanything but GET or HEAD.

For optimal performance when handling range requests, it’s recommendedthat your response data object implementsseekable,seek andtellmethods as described byio.IOBase. Objects returned bywrap_file() automatically implement those methods.

It does not remove the body of the response because that’s somethingthe__call__() function does for us automatically.

Returns self so that you can doreturnresp.make_conditional(req)but modifies the object in-place.

Parameters:

request_or_environ (WSGIEnvironment |Request) – a request object or WSGI environment to beused to make the response conditionalagainst.
accept_ranges (bool |str) – This parameter dictates the value ofAccept-Ranges header. IfFalse (default),the header is not set. IfTrue, it will be setto"bytes". If it’s a string, it will use thisvalue.
complete_length (int |None) – Will be used only in valid Range Requests.It will setContent-Range complete lengthvalue and computeContent-Length real value.This parameter is mandatory for successfulRange Requests completion.

Raises:

RequestedRangeNotSatisfiableifRange header could not be parsed or satisfied.

Return type:

Changelog

Changed in version 2.0:Range processing is skipped if length is 0 instead ofraising a 416 Range Not Satisfiable error.

make_sequence()¶

Converts the response iterator in a list. By default this happensautomatically if required. Ifimplicit_sequence_conversion isdisabled, this method is not automatically called and some propertiesmight raise exceptions. This also encodes all the items.

Changelog

Added in version 0.6.

Return type:: None

propertymimetype:str|None¶: The mimetype (content type without charset etc.)

propertymimetype_params:dict[str,str]¶: The mimetype parameters as dict. For example if thecontent type istext/html;charset=utf-8 the params would be{'charset':'utf-8'}.
Changelog
Added in version 0.5.

propertyretry_after:datetime|None¶

The Retry-After response-header field can be used with a503 (Service Unavailable) response to indicate how long theservice is expected to be unavailable to the requesting client.

Time in seconds until expiration or date.

Changelog

Changed in version 2.0:The datetime object is timezone-aware.

set_cookie(key,value='',max_age=None,expires=None,path='/',domain=None,secure=False,httponly=False,samesite=None,partitioned=False)¶

Sets a cookie.

A warning is raised if the size of the cookie header exceedsmax_cookie_size, but the header will still be set.

Parameters:

key (str) – the key (name) of the cookie to be set.
value (str) – the value of the cookie.
max_age (timedelta |int |None) – should be a number of seconds, orNone (default) ifthe cookie should last only as long as the client’sbrowser session.
expires (str |datetime |int |float |None) – should be adatetime object or UNIX timestamp.
path (str |None) – limits the cookie to a given path, per default it willspan the whole domain.
domain (str |None) – if you want to set a cross-domain cookie. For example,domain="example.com" will set a cookie that isreadable by the domainwww.example.com,foo.example.com etc. Otherwise, a cookie will onlybe readable by the domain that set it.
secure (bool) – IfTrue, the cookie will only be availablevia HTTPS.
httponly (bool) – Disallow JavaScript access to the cookie.
samesite (str |None) – Limit the scope of the cookie to only beattached to requests that are “same-site”.
partitioned (bool) – IfTrue, the cookie will be partitioned.

Return type:

None

Changed in version 3.1:Thepartitioned parameter was added.

set_data(value)¶

Sets a new string as response. The value must be a string orbytes. If a string is set it’s encoded to the charset of theresponse (utf-8 by default).

Changelog

Added in version 0.9.

Parameters:: value (bytes |str)
Return type:: None

set_etag(etag,weak=False)¶

Set the etag, and override the old one if there was one.

Parameters:

etag (str)
weak (bool)

Return type:

None

propertystatus:str¶: The HTTP status code as a string.

propertystatus_code:int¶: The HTTP status code as a number.

propertystream:ResponseStream¶: The response iterable as write-only stream.

propertyvary:HeaderSet¶: The Vary field value indicates the set of request-headerfields that fully determines, while the response is fresh,whether a cache is permitted to use the response to reply to asubsequent request without revalidation.

propertywww_authenticate:WWWAuthenticate¶

TheWWW-Authenticate header parsed into aWWWAuthenticateobject. Modifying the object will modify the header value.

This header is not set by default. To set this header, assign an instance ofWWWAuthenticate to this attribute.

response.www_authenticate=WWWAuthenticate("basic",{"realm":"Authentication Required"})

Multiple values for this header can be sent to give the client multiple options.Assign a list to set multiple headers. However, modifying the items in the listwill not automatically update the header values, and accessing this attributewill only ever return the first value.

To unset this header, assignNone or usedel.

Changelog

Changed in version 2.3:This attribute can be assigned to to set the header. A list can be assignedto set multiple header values. Usedel to unset the header.

Changed in version 2.3:WWWAuthenticate is no longer adict. Thetoken attributewas added for auth challenges that use a token instead of parameters.

response:t.Iterable[str]|t.Iterable[bytes]¶

The response body to send as the WSGI iterable. A list of stringsor bytes represents a fixed-length response, any other iterableis a streaming response. Strings are encoded to bytes as UTF-8.

Do not set to a plain string or bytes, that will cause sendingthe response to be very inefficient as it will iterate one byteat a time.

direct_passthrough¶: Pass the response body directly through as the WSGI iterable.This can be used when the body is a binary file or otheriterator of bytes, to skip some unnecessary checks. Usesend_file() instead of setting thismanually.

autocorrect_location_header=False¶: If a redirectLocation header is a relative URL, make it anabsolute URL, including scheme and domain.
Changelog
Changed in version 2.1:This is disabled by default, so responses will send relativeredirects.
Added in version 0.8.

propertymax_cookie_size:int¶

Read-only view of theMAX_COOKIE_SIZE config key.

Seemax_cookie_size inWerkzeug’s docs.

Sessions¶

If you have setFlask.secret_key (or configured it fromSECRET_KEY) you can use sessions in Flask applications. A session makesit possible to remember information from one request to another. The way Flaskdoes this is by using a signed cookie. The user can look at the sessioncontents, but can’t modify it unless they know the secret key, so make sure toset that to something complex and unguessable.

To access the current session you can use thesession object:

classflask.session¶

The session object works pretty much like an ordinary dict, with thedifference that it keeps track of modifications.

This is a proxy. SeeNotes On Proxies for more information.

The following attributes are interesting:

new¶: True if the session is new,False otherwise.

modified¶

True if the session object detected a modification. Be advisedthat modifications on mutable structures are not picked upautomatically, in that situation you have to explicitly set theattribute toTrue yourself. Here an example:

# this change is not picked up because a mutable object (here# a list) is changed.session['objects'].append(42)# so mark it as modified yourselfsession.modified=True

permanent¶: If set toTrue the session lives forpermanent_session_lifetime seconds. Thedefault is 31 days. If set toFalse (which is the default) thesession will be deleted when the user closes the browser.

Session Interface¶

Changelog

Added in version 0.8.

The session interface provides a simple way to replace the sessionimplementation that Flask is using.

classflask.sessions.SessionInterface¶

The basic interface you have to implement in order to replace thedefault session interface which uses werkzeug’s securecookieimplementation. The only methods you have to implement areopen_session() andsave_session(), the others haveuseful defaults which you don’t need to change.

The session object returned by theopen_session() method has toprovide a dictionary like interface plus the properties and methodsfrom theSessionMixin. We recommend just subclassing a dictand adding that mixin:

classSession(dict,SessionMixin):pass

Ifopen_session() returnsNone Flask will call intomake_null_session() to create a session that acts as replacementif the session support cannot work because some requirement is notfulfilled. The defaultNullSession class that is createdwill complain that the secret key was not set.

To replace the session interface on an application all you have to dois to assignflask.Flask.session_interface:

app=Flask(__name__)app.session_interface=MySessionInterface()

Multiple requests with the same session may be sent and handledconcurrently. When implementing a new session interface, considerwhether reads or writes to the backing store must be synchronized.There is no guarantee on the order in which the session for eachrequest is opened or saved, it will occur in the order that requestsbegin and end processing.

Changelog

Added in version 0.8.

null_session_class¶

make_null_session() will look here for the class that shouldbe created when a null session is requested. Likewise theis_null_session() method will perform a typecheck againstthis type.

alias ofNullSession

pickle_based=False¶: A flag that indicates if the session interface is pickle based.This can be used by Flask extensions to make a decision in regardsto how to deal with the session object.
Changelog
Added in version 0.10.

make_null_session(app)¶

Creates a null session which acts as a replacement object if thereal session support could not be loaded due to a configurationerror. This mainly aids the user experience because the job of thenull session is to still support lookup without complaining butmodifications are answered with a helpful error message of whatfailed.

This creates an instance ofnull_session_class by default.

Parameters:: app (Flask)
Return type:: NullSession

is_null_session(obj)¶

Checks if a given object is a null session. Null sessions arenot asked to be saved.

This checks if the object is an instance ofnull_session_classby default.

Parameters:: obj (object)
Return type:: bool

get_cookie_name(app)¶

The name of the session cookie. Uses``app.config[“SESSION_COOKIE_NAME”]``.

Parameters:: app (Flask)
Return type:: str

get_cookie_domain(app)¶

The value of theDomain parameter on the session cookie. If not set,browsers will only send the cookie to the exact domain it was set from.Otherwise, they will send it to any subdomain of the given value as well.

Uses theSESSION_COOKIE_DOMAIN config.

Changelog

Changed in version 2.3:Not set by default, does not fall back toSERVER_NAME.

Parameters:: app (Flask)
Return type:: str | None

get_cookie_path(app)¶

Returns the path for which the cookie should be valid. Thedefault implementation uses the value from theSESSION_COOKIE_PATHconfig var if it’s set, and falls back toAPPLICATION_ROOT oruses/ if it’sNone.

Parameters:: app (Flask)
Return type:: str

get_cookie_httponly(app)¶

Returns True if the session cookie should be httponly. Thiscurrently just returns the value of theSESSION_COOKIE_HTTPONLYconfig var.

Parameters:: app (Flask)
Return type:: bool

get_cookie_secure(app)¶

Returns True if the cookie should be secure. This currentlyjust returns the value of theSESSION_COOKIE_SECURE setting.

Parameters:: app (Flask)
Return type:: bool

get_cookie_samesite(app)¶

Return'Strict' or'Lax' if the cookie should use theSameSite attribute. This currently just returns the value oftheSESSION_COOKIE_SAMESITE setting.

Parameters:: app (Flask)
Return type:: str | None

get_cookie_partitioned(app)¶

Returns True if the cookie should be partitioned. By default, usesthe value ofSESSION_COOKIE_PARTITIONED.

Added in version 3.1.

Parameters:: app (Flask)
Return type:: bool

get_expiration_time(app,session)¶

A helper method that returns an expiration date for the sessionorNone if the session is linked to the browser session. Thedefault implementation returns now + the permanent sessionlifetime configured on the application.

Parameters:

app (Flask)
session (SessionMixin)

Return type:

datetime | None

should_set_cookie(app,session)¶

Used by session backends to determine if aSet-Cookie headershould be set for this session cookie for this response. If the sessionhas been modified, the cookie is set. If the session is permanent andtheSESSION_REFRESH_EACH_REQUEST config is true, the cookie isalways set.

This check is usually skipped if the session was deleted.

Changelog

Added in version 0.11.

Parameters:

app (Flask)
session (SessionMixin)

Return type:

open_session(app,request)¶

This is called at the beginning of each request, afterpushing the request context, before matching the URL.

This must return an object which implements a dictionary-likeinterface as well as theSessionMixin interface.

This will returnNone to indicate that loading failed insome way that is not immediately an error. The requestcontext will fall back to usingmake_null_session()in this case.

Parameters:

app (Flask)
request (Request)

Return type:

SessionMixin | None

save_session(app,session,response)¶

This is called at the end of each request, after generatinga response, before removing the request context. It is skippedifis_null_session() returnsTrue.

Parameters:

app (Flask)
session (SessionMixin)
response (Response)

Return type:

None

classflask.sessions.SecureCookieSessionInterface¶

The default session interface that stores sessions in signed cookiesthrough theitsdangerous module.

salt='cookie-session'¶: the salt that should be applied on top of the secret key for thesigning of cookie based sessions.

staticdigest_method(string=b'')¶

the hash function to use for the signature. The default is sha1

Parameters:: string (bytes)
Return type:: Any

key_derivation='hmac'¶: the name of the itsdangerous supported key derivation. The defaultis hmac.

serializer=<flask.json.tag.TaggedJSONSerializerobject>¶: A python serializer for the payload. The default is a compactJSON derived serializer with support for some extra Python typessuch as datetime objects or tuples.

session_class¶: alias ofSecureCookieSession

open_session(app,request)¶

This is called at the beginning of each request, afterpushing the request context, before matching the URL.

This must return an object which implements a dictionary-likeinterface as well as theSessionMixin interface.

This will returnNone to indicate that loading failed insome way that is not immediately an error. The requestcontext will fall back to usingmake_null_session()in this case.

Parameters:

app (Flask)
request (Request)

Return type:

SecureCookieSession | None

save_session(app,session,response)¶

This is called at the end of each request, after generatinga response, before removing the request context. It is skippedifis_null_session() returnsTrue.

Parameters:

app (Flask)
session (SessionMixin)
response (Response)

Return type:

None

classflask.sessions.SecureCookieSession(initial=None)¶

Base class for sessions based on signed cookies.

This session backend will set themodified andaccessed attributes. It cannot reliably track whether asession is new (vs. empty), sonew remains hard coded toFalse.

Parameters:: initial (c.Mapping[str,t.Any]|c.Iterable[tuple[str,t.Any]]|None)

modified=False¶: When data is changed, this is set toTrue. Only the sessiondictionary itself is tracked; if the session contains mutabledata (for example a nested dict) then this must be set toTrue manually when modifying that data. The session cookiewill only be written to the response if this isTrue.

accessed=False¶: header, which allows caching proxies to cache different pages fordifferent users.

get(key,default=None)¶

Return the value for key if key is in the dictionary, else default.

Parameters:

key (str)
default (Any)

Return type:

setdefault(key,default=None)¶

Insert key with a value of default if key is not in the dictionary.

Return the value for key if key is in the dictionary, else default.

Parameters:

key (str)
default (Any)

Return type:

classflask.sessions.NullSession(initial=None)¶

Class used to generate nicer error messages if sessions are notavailable. Will still allow read-only access to the empty sessionbut fail on setting.

Parameters:: initial (c.Mapping[str,t.Any]|c.Iterable[tuple[str,t.Any]]|None)

clear(*args,**kwargs)¶

Remove all items from the dict.

Parameters:

args (Any)
kwargs (Any)

Return type:

pop(k[,d])→v,removespecifiedkeyandreturnthecorrespondingvalue.¶

If the key is not found, return the default if given; otherwise,raise a KeyError.

Parameters:

args (Any)
kwargs (Any)

Return type:

popitem(*args,**kwargs)¶

Remove and return a (key, value) pair as a 2-tuple.

Pairs are returned in LIFO (last-in, first-out) order.Raises KeyError if the dict is empty.

Parameters:

args (Any)
kwargs (Any)

Return type:

update([E,]**F)→None. UpdateDfrommapping/iterableEandF.¶

If E is present and has a .keys() method, then does: for k in E.keys(): D[k] = E[k]If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = vIn either case, this is followed by: for k in F: D[k] = F[k]

Parameters:

args (Any)
kwargs (Any)

Return type:

setdefault(*args,**kwargs)¶

Insert key with a value of default if key is not in the dictionary.

Return the value for key if key is in the dictionary, else default.

Parameters:

args (Any)
kwargs (Any)

Return type:

Iterator[SessionMixin]

classflask.sessions.SessionMixin¶

Expands a basic dictionary with session attributes.

propertypermanent:bool¶: This reflects the'_permanent' key in the dict.

modified=True¶: Some implementations can detect changes to the session and setthis when that happens. The mixin default is hard coded toTrue.

accessed=True¶: Some implementations can detect when session data is read orwritten and set this when that happens. The mixin default is hardcoded toTrue.

Notice

ThePERMANENT_SESSION_LIFETIME config can be an integer ortimedelta.Thepermanent_session_lifetime attribute is always atimedelta.

Test Client¶

classflask.testing.FlaskClient(*args,**kwargs)¶

Works like a regular Werkzeug test client but has knowledge aboutFlask’s contexts to defer the cleanup of the request context untilthe end of awith block. For general information about how touse this class refer towerkzeug.test.Client.

Changelog

Changed in version 0.12:app.test_client() includes preset default environment, which can beset after instantiation of theapp.test_client() object inclient.environ_base.

Basic usage is outlined in theTesting Flask Applications chapter.

Parameters:

args (t.Any)
kwargs (t.Any)

session_transaction(*args,**kwargs)¶

When used in combination with awith statement this opens asession transaction. This can be used to modify the session thatthe test client uses. Once thewith block is left the session isstored back.

withclient.session_transaction()assession:session['value']=42

Internally this is implemented by going through a temporary testrequest context and since session handling could depend onrequest variables this function accepts the same arguments astest_request_context() which are directlypassed through.

Parameters:

args (Any)
kwargs (Any)

Return type:

open(*args,buffered=False,follow_redirects=False,**kwargs)¶

Generate an environ dict from the given arguments, make arequest to the application using it, and return the response.

Parameters:

args (t.Any) – Passed toEnvironBuilder to create theenviron for the request. If a single arg is passed, it canbe an existingEnvironBuilder or an environ dict.
buffered (bool) – Convert the iterator returned by the app intoa list. If the iterator has aclose() method, it iscalled automatically.
follow_redirects (bool) – Make additional requests to follow HTTPredirects until a non-redirect status is returned.TestResponse.history lists the intermediateresponses.
kwargs (t.Any)

Return type:

TestResponse

Changelog

Changed in version 2.1:Removed theas_tuple parameter.

Changed in version 2.0:The request input stream is closed when callingresponse.close(). Input streams for redirects areautomatically closed.

Changed in version 0.5:If a dict is provided as file in the dict for thedataparameter the content type has to be calledcontent_typeinstead ofmimetype. This change was made forconsistency withwerkzeug.FileWrapper.

Changed in version 0.5:Added thefollow_redirects parameter.

Test CLI Runner¶

classflask.testing.FlaskCliRunner(app,**kwargs)¶

ACliRunner for testing a Flask app’sCLI commands. Typically created usingtest_cli_runner(). SeeRunning Commands with the CLI Runner.

Parameters:

app (Flask)
kwargs (t.Any)

invoke(cli=None,args=None,**kwargs)¶

Invokes a CLI command in an isolated environment. SeeCliRunner.invoke forfull method documentation. SeeRunning Commands with the CLI Runner for examples.

If theobj argument is not given, passes an instance ofScriptInfo that knows how to load the Flaskapp being tested.

Parameters:

cli (Any) – Command object to invoke. Default is the app’scli group.
args (Any) – List of strings to invoke the command with.
kwargs (Any)

Returns:

aResult object.

Return type:

Result

Application Globals¶

To share data that is valid for one request only from one function toanother, a global variable is not good enough because it would break inthreaded environments. Flask provides you with a special object thatensures it is only valid for the active request and that will returndifferent values for each request. In a nutshell: it does the rightthing, like it does forrequest andsession.

flask.g¶

A namespace object that can store data during anapplication context. This is an instance ofFlask.app_ctx_globals_class, which defaults toctx._AppCtxGlobals.

This is a good place to store resources during a request. Forexample, abefore_request function could load a user object froma session id, then setg.user to be used in the view function.

This is a proxy. SeeNotes On Proxies for more information.

Changelog

Changed in version 0.10:Bound to the application context instead of the request context.

classflask.ctx._AppCtxGlobals¶

A plain object. Used as a namespace for storing data during anapplication context.

Creating an app context automatically creates this object, which ismade available as theg proxy.

'key'ing: Check whether an attribute is present.
Changelog
Added in version 0.10.

iter(g): Return an iterator over the attribute names.
Changelog
Added in version 0.10.

get(name,default=None)¶

Get an attribute by name, or a default value. Likedict.get().

Parameters:

name (str) – Name of attribute to get.
default (Any |None) – Value to return if the attribute is not present.

Return type:

Changelog

Added in version 0.10.

pop(name,default=_sentinel)¶

Get and remove an attribute by name. Likedict.pop().

Parameters:

name (str) – Name of attribute to pop.
default (Any) – Value to return if the attribute is not present,instead of raising aKeyError.

Return type:

Changelog

Added in version 0.11.

setdefault(name,default=None)¶

Get the value of an attribute if it is present, otherwiseset and return a default value. Likedict.setdefault().

Parameters:

name (str) – Name of attribute to get.
default (Any) – Value to set and return if the attribute is notpresent.

Return type:

Changelog

Added in version 0.11.

Useful Functions and Classes¶

flask.current_app¶

A proxy to the application handling the current request. This isuseful to access the application without needing to import it, or ifit can’t be imported, such as when using the application factorypattern or in blueprints and extensions.

This is only available when anapplication context is pushed. This happensautomatically during requests and CLI commands. It can be controlledmanually withapp_context().

This is a proxy. SeeNotes On Proxies for more information.

flask.has_request_context()¶

If you have code that wants to test if a request context is there ornot this function can be used. For instance, you may want to take advantageof request information if the request object is available, but failsilently if it is unavailable.

classUser(db.Model):def__init__(self,username,remote_addr=None):self.username=usernameifremote_addrisNoneandhas_request_context():remote_addr=request.remote_addrself.remote_addr=remote_addr

Alternatively you can also just test any of the context bound objects(such asrequest org) for truthness:

classUser(db.Model):def__init__(self,username,remote_addr=None):self.username=usernameifremote_addrisNoneandrequest:remote_addr=request.remote_addrself.remote_addr=remote_addr

Changelog

Added in version 0.7.

Return type:: bool

flask.copy_current_request_context(f)¶

A helper function that decorates a function to retain the currentrequest context. This is useful when working with greenlets. The momentthe function is decorated a copy of the request context is created andthen pushed when the function is called. The current session is alsoincluded in the copied request context.

Example:

importgeventfromflaskimportcopy_current_request_context@app.route('/')defindex():@copy_current_request_contextdefdo_some_work():# do some work here, it can access flask.request or# flask.session like you would otherwise in the view function....gevent.spawn(do_some_work)return'Regular response'

Changelog

Added in version 0.10.

Parameters:: f (F)
Return type:: F

flask.has_app_context()¶

Works likehas_request_context() but for the applicationcontext. You can also just do a boolean check on thecurrent_app object instead.

Changelog

Added in version 0.9.

Return type:: bool

flask.url_for(endpoint,*,_anchor=None,_method=None,_scheme=None,_external=None,**values)¶

Generate a URL to the given endpoint with the given values.

This requires an active request or application context, and callscurrent_app.url_for(). See that methodfor full documentation.

Parameters:

endpoint (str) – The endpoint name associated with the URL togenerate. If this starts with a., the current blueprintname (if any) will be used.
_anchor (str |None) – If given, append this as#anchor to the URL.
_method (str |None) – If given, generate the URL associated with thismethod for the endpoint.
_scheme (str |None) – If given, the URL will have this scheme if it isexternal.
_external (bool |None) – If given, prefer the URL to be internal (False) orrequire it to be external (True). External URLs include thescheme and domain. When not in an active request, URLs areexternal by default.
values (Any) – Values to use for the variable parts of the URL rule.Unknown keys are appended as query string arguments, like?a=b&c=d.

Return type:

Changelog

Changed in version 2.2:Callscurrent_app.url_for, allowing an app to override thebehavior.

Changed in version 0.10:The_scheme parameter was added.

Changed in version 0.9:The_anchor and_method parameters were added.

Changed in version 0.9:Callsapp.handle_url_build_error on build errors.

flask.abort(code,*args,**kwargs)¶

Raise anHTTPException for the givenstatus code.

Ifcurrent_app is available, it will call itsaborter object, otherwise it will usewerkzeug.exceptions.abort().

Parameters:

code (int |Response) – The status code for the exception, which must beregistered inapp.aborter.
args (Any) – Passed to the exception.
kwargs (Any) – Passed to the exception.

Return type:

Changelog

Added in version 2.2:Callscurrent_app.aborter if available instead of alwaysusing Werkzeug’s defaultabort.

flask.redirect(location,code=302,Response=None)¶

Create a redirect response object.

Ifcurrent_app is available, it will use itsredirect() method, otherwise it will usewerkzeug.utils.redirect().

Parameters:

location (str) – The URL to redirect to.
code (int) – The status code for the redirect.
Response (type[Response]|None) – The response class to use. Not used whencurrent_app is active, which usesapp.response_class.

Return type:

Response

Changelog

Added in version 2.2:Callscurrent_app.redirect if available instead of alwaysusing Werkzeug’s defaultredirect.

flask.make_response(*args)¶

Sometimes it is necessary to set additional headers in a view. Becauseviews do not have to return response objects but can return a value thatis converted into a response object by Flask itself, it becomes tricky toadd headers to it. This function can be called instead of using a returnand you will get a response object which you can use to attach headers.

If view looked like this and you want to add a new header:

defindex():returnrender_template('index.html',foo=42)

You can now do something like this:

defindex():response=make_response(render_template('index.html',foo=42))response.headers['X-Parachutes']='parachutes are cool'returnresponse

This function accepts the very same arguments you can return from aview function. This for example creates a response with a 404 errorcode:

response=make_response(render_template('not_found.html'),404)

The other use case of this function is to force the return value of aview function into a response which is helpful with viewdecorators:

response=make_response(view_function())response.headers['X-Parachutes']='parachutes are cool'

Internally this function does the following things:

if no arguments are passed, it creates a new response argument
if one argument is passed,flask.Flask.make_response()is invoked with it.
if more than one argument is passed, the arguments are passedto theflask.Flask.make_response() function as tuple.

Changelog

Added in version 0.6.

Parameters:: args (t.Any)
Return type:: Response

flask.after_this_request(f)¶

Executes a function after this request. This is useful to modifyresponse objects. The function is passed the response object and hasto return the same or a new one.

Example:

@app.route('/')defindex():@after_this_requestdefadd_header(response):response.headers['X-Foo']='Parachute'returnresponsereturn'Hello World!'

This is more useful if a function other than the view function wants tomodify a response. For instance think of a decorator that wants to addsome headers without converting the return value into a response object.

Changelog

Added in version 0.9.

Parameters:: f (Callable[[Any],Any]|Callable[[Any],Awaitable[Any]])
Return type:: Callable[[Any],Any] |Callable[[Any],Awaitable[Any]]

flask.send_file(path_or_file,mimetype=None,as_attachment=False,download_name=None,conditional=True,etag=True,last_modified=None,max_age=None)¶

Send the contents of a file to the client.

The first argument can be a file path or a file-like object. Pathsare preferred in most cases because Werkzeug can manage the file andget extra information from the path. Passing a file-like objectrequires that the file is opened in binary mode, and is mostlyuseful when building a file in memory withio.BytesIO.

Never pass file paths provided by a user. The path is assumed to betrusted, so a user could craft a path to access a file you didn’tintend. Usesend_from_directory() to safely serveuser-requested paths from within a directory.

If the WSGI server sets afile_wrapper inenviron, it isused, otherwise Werkzeug’s built-in wrapper is used. Alternatively,if the HTTP server supportsX-Sendfile, configuring Flask withUSE_X_SENDFILE=True will tell the server to send the givenpath, which is much more efficient than reading it in Python.

Parameters:

path_or_file (os.PathLike[t.AnyStr]|str |t.IO[bytes]) – The path to the file to send, relative to thecurrent working directory if a relative path is given.Alternatively, a file-like object opened in binary mode. Makesure the file pointer is seeked to the start of the data.
mimetype (str |None) – The MIME type to send for the file. If notprovided, it will try to detect it from the file name.
as_attachment (bool) – Indicate to a browser that it should offer tosave the file instead of displaying it.
download_name (str |None) – The default name browsers will use when savingthe file. Defaults to the passed file name.
conditional (bool) – Enable conditional and range responses based onrequest headers. Requires passing a file path andenviron.
etag (bool |str) – Calculate an ETag for the file, which requires passinga file path. Can also be a string to use instead.
last_modified (datetime |int |float |None) – The last modified time to send for the file,in seconds. If not provided, it will try to detect it from thefile path.
max_age (None |(int |t.Callable[[str |None],int |None])) – How long the client should cache the file, inseconds. If set,Cache-Control will bepublic, otherwiseit will beno-cache to prefer conditional caching.

Return type:

Changelog

Changed in version 2.0:download_name replaces theattachment_filenameparameter. Ifas_attachment=False, it is passed withContent-Disposition:inline instead.

Changed in version 2.0:max_age replaces thecache_timeout parameter.conditional is enabled andmax_age is not set bydefault.

Changed in version 2.0:etag replaces theadd_etags parameter. It can be astring to use instead of generating one.

Changed in version 2.0:Passing a file-like object that inherits fromTextIOBase will raise aValueError ratherthan sending an empty file.

Added in version 2.0:Moved the implementation to Werkzeug. This is now a wrapper topass some Flask-specific arguments.

Changed in version 1.1:filename may be aPathLike object.

Changed in version 1.1:Passing aBytesIO object supports range requests.

Changed in version 1.0.3:Filenames are encoded with ASCII instead of Latin-1 for broadercompatibility with WSGI servers.

Changed in version 1.0:UTF-8 filenames as specified inRFC 2231 are supported.

Changed in version 0.12:The filename is no longer automatically inferred from fileobjects. If you want to use automatic MIME and etag support,pass a filename viafilename_or_fp orattachment_filename.

Changed in version 0.12:attachment_filename is preferred overfilename for MIMEdetection.

Changed in version 0.9:cache_timeout defaults toFlask.get_send_file_max_age().

Changed in version 0.7:MIME guessing and etag support for file-like objects wasremoved because it was unreliable. Pass a filename if you areable to, otherwise attach an etag yourself.

Changed in version 0.5:Theadd_etags,cache_timeout andconditionalparameters were added. The default behavior is to add etags.

Added in version 0.2.

flask.send_from_directory(directory,path,**kwargs)¶

Send a file from within a directory usingsend_file().

@app.route("/uploads/<path:name>")defdownload_file(name):returnsend_from_directory(app.config['UPLOAD_FOLDER'],name,as_attachment=True)

This is a secure way to serve files from a folder, such as staticfiles or uploads. Usessafe_join() toensure the path coming from the client is not maliciously crafted topoint outside the specified directory.

If the final path does not point to an existing regular file,raises a 404NotFound error.

Parameters:

directory (os.PathLike[str]|str) – The directory thatpath must be located under,relative to the current application’s root path. Thismust notbe a value provided by the client, otherwise it becomes insecure.
path (os.PathLike[str]|str) – The path to the file to send, relative todirectory.
kwargs (t.Any) – Arguments to pass tosend_file().

Return type:

Changelog

Changed in version 2.0:path replaces thefilename parameter.

Added in version 2.0:Moved the implementation to Werkzeug. This is now a wrapper topass some Flask-specific arguments.

Added in version 0.5.

Message Flashing¶

flask.flash(message,category='message')¶

Flashes a message to the next request. In order to remove theflashed message from the session and to display it to the user,the template has to callget_flashed_messages().

Changelog

Changed in version 0.3:category parameter added.

Parameters:

message (str) – the message to be flashed.
category (str) – the category for the message. The following valuesare recommended:'message' for any kind of message,'error' for errors,'info' for informationmessages and'warning' for warnings. However anykind of string can be used as category.

Return type:

None

flask.get_flashed_messages(with_categories=False,category_filter=())¶

Pulls all flashed messages from the session and returns them.Further calls in the same request to the function will returnthe same messages. By default just the messages are returned,but whenwith_categories is set toTrue, the return value willbe a list of tuples in the form(category,message) instead.

Filter the flashed messages to one or more categories by providing thosecategories incategory_filter. This allows rendering categories inseparate html blocks. Thewith_categories andcategory_filterarguments are distinct:

with_categories controls whether categories are returned with messagetext (True gives a tuple, whereFalse gives just the message text).
category_filter filters the messages down to only those matching theprovided categories.

SeeMessage Flashing for examples.

Changelog

Changed in version 0.9:category_filter parameter added.

Changed in version 0.3:with_categories parameter added.

Parameters:

with_categories (bool) – set toTrue to also receive categories.
category_filter (Iterable[str]) – filter of categories to limit return values. Onlycategories in the list will be returned.

Return type:

list[str] |list[tuple[str,str]]

JSON Support¶

Flask uses Python’s built-injson module for handling JSON bydefault. The JSON implementation can be changed by assigning a differentprovider toflask.Flask.json_provider_class orflask.Flask.json. The functions provided byflask.json willuse methods onapp.json if an app context is active.

Jinja’s|tojson filter is configured to use the app’s JSON provider.The filter marks the output with|safe. Use it to render data insideHTML<script> tags.

<script>constnames={{names|tojson}};renderChart(names,{{axis_data|tojson}});</script>

flask.json.jsonify(*args,**kwargs)¶

Serialize the given arguments as JSON, and return aResponse object with theapplication/jsonmimetype. A dict or list returned from a view will be converted to aJSON response automatically without needing to call this.

This requires an active request or application context, and callsapp.json.response().

In debug mode, the output is formatted with indentation to make iteasier to read. This may also be controlled by the provider.

Either positional or keyword arguments can be given, not both.If no arguments are given,None is serialized.

Parameters:

args (t.Any) – A single value to serialize, or multiple values totreat as a list to serialize.
kwargs (t.Any) – Treat as a dict to serialize.

Return type:

Changelog

Changed in version 2.2:Callscurrent_app.json.response, allowing an app to overridethe behavior.

Changed in version 2.0.2:decimal.Decimal is supported by converting to a string.

Changed in version 0.11:Added support for serializing top-level arrays. This was asecurity risk in ancient browsers. SeeJSON Security.

Added in version 0.2.

flask.json.dumps(obj,**kwargs)¶

Serialize data as JSON.

Ifcurrent_app is available, it will use itsapp.json.dumps()method, otherwise it will usejson.dumps().

Parameters:

obj (Any) – The data to serialize.
kwargs (Any) – Arguments passed to thedumps implementation.

Return type:

Changelog

Changed in version 2.3:Theapp parameter was removed.

Changed in version 2.2:Callscurrent_app.json.dumps, allowing an app to overridethe behavior.

Changed in version 2.0.2:decimal.Decimal is supported by converting to a string.

Changed in version 2.0:encoding will be removed in Flask 2.1.

Changed in version 1.0.3:app can be passed directly, rather than requiring an appcontext for configuration.

flask.json.dump(obj,fp,**kwargs)¶

Serialize data as JSON and write to a file.

Ifcurrent_app is available, it will use itsapp.json.dump()method, otherwise it will usejson.dump().

Parameters:

obj (Any) – The data to serialize.
fp (IO[str]) – A file opened for writing text. Should use the UTF-8encoding to be valid JSON.
kwargs (Any) – Arguments passed to thedump implementation.

Return type:

None

Changelog

Changed in version 2.3:Theapp parameter was removed.

Changed in version 2.2:Callscurrent_app.json.dump, allowing an app to overridethe behavior.

Changed in version 2.0:Writing to a binary file, and theencoding argument, will beremoved in Flask 2.1.

flask.json.loads(s,**kwargs)¶

Deserialize data as JSON.

Ifcurrent_app is available, it will use itsapp.json.loads()method, otherwise it will usejson.loads().

Parameters:

s (str |bytes) – Text or UTF-8 bytes.
kwargs (Any) – Arguments passed to theloads implementation.

Return type:

Changelog

Changed in version 2.3:Theapp parameter was removed.

Changed in version 2.2:Callscurrent_app.json.loads, allowing an app to overridethe behavior.

Changed in version 2.0:encoding will be removed in Flask 2.1. The data must be astring or UTF-8 bytes.

Changed in version 1.0.3:app can be passed directly, rather than requiring an appcontext for configuration.

flask.json.load(fp,**kwargs)¶

Deserialize data as JSON read from a file.

Ifcurrent_app is available, it will use itsapp.json.load()method, otherwise it will usejson.load().

Parameters:

fp (IO) – A file opened for reading text or UTF-8 bytes.
kwargs (Any) – Arguments passed to theload implementation.

Return type:

Changelog

Changed in version 2.3:Theapp parameter was removed.

Changed in version 2.2:Callscurrent_app.json.load, allowing an app to overridethe behavior.

Changed in version 2.2:Theapp parameter will be removed in Flask 2.3.

Changed in version 2.0:encoding will be removed in Flask 2.1. The file must be textmode, or binary mode with UTF-8 bytes.

classflask.json.provider.JSONProvider(app)¶

A standard set of JSON operations for an application. Subclassesof this can be used to customize JSON behavior or use differentJSON libraries.

To implement a provider for a specific library, subclass this baseclass and implement at leastdumps() andloads(). Allother methods have default implementations.

To use a different provider, either subclassFlask and setjson_provider_class to a provider class, or setapp.json to an instance of the class.

Parameters:: app (App) – An application instance. This will be stored as aweakref.proxy on the_app attribute.

Changelog

Added in version 2.2.

dumps(obj,**kwargs)¶

Serialize data as JSON.

Parameters:

obj (Any) – The data to serialize.
kwargs (Any) – May be passed to the underlying JSON library.

Return type:

dump(obj,fp,**kwargs)¶

Serialize data as JSON and write to a file.

Parameters:

obj (Any) – The data to serialize.
fp (IO[str]) – A file opened for writing text. Should use the UTF-8encoding to be valid JSON.
kwargs (Any) – May be passed to the underlying JSON library.

Return type:

None

loads(s,**kwargs)¶

Deserialize data as JSON.

Parameters:

s (str |bytes) – Text or UTF-8 bytes.
kwargs (Any) – May be passed to the underlying JSON library.

Return type:

load(fp,**kwargs)¶

Deserialize data as JSON read from a file.

Parameters:

fp (IO) – A file opened for reading text or UTF-8 bytes.
kwargs (Any) – May be passed to the underlying JSON library.

Return type:

response(*args,**kwargs)¶

Serialize the given arguments as JSON, and return aResponse object with theapplication/jsonmimetype.

Thejsonify() function calls this method forthe current application.

Either positional or keyword arguments can be given, not both.If no arguments are given,None is serialized.

Parameters:

args (t.Any) – A single value to serialize, or multiple values totreat as a list to serialize.
kwargs (t.Any) – Treat as a dict to serialize.

Return type:

classflask.json.provider.DefaultJSONProvider(app)¶

Provide JSON operations using Python’s built-injsonlibrary. Serializes the following additional data types:

datetime.datetime anddatetime.date areserialized toRFC 822 strings. This is the same as the HTTPdate format.
uuid.UUID is serialized to a string.
dataclasses.dataclass is passed todataclasses.asdict().
Markup (or any object with a__html__method) will call the__html__ method to get a string.

Parameters:: app (App)

staticdefault(o)¶

Apply this function to any object thatjson.dumps() doesnot know how to serialize. It should return a valid JSON type orraise aTypeError.

Parameters:: o (Any)
Return type:: Any

ensure_ascii=True¶: Replace non-ASCII characters with escape sequences. This may bemore compatible with some clients, but can be disabled for betterperformance and size.

sort_keys=True¶: Sort the keys in any serialized dicts. This may be useful forsome caching situations, but can be disabled for better performance.When enabled, keys must all be strings, they are not convertedbefore sorting.

compact:bool|None=None¶: IfTrue, orNone out of debug mode, theresponse()output will not add indentation, newlines, or spaces. IfFalse,orNone in debug mode, it will use a non-compact representation.

mimetype='application/json'¶: The mimetype set inresponse().

dumps(obj,**kwargs)¶

Serialize data as JSON to a string.

Keyword arguments are passed tojson.dumps(). Sets someparameter defaults from thedefault,ensure_ascii, andsort_keys attributes.

Parameters:

obj (Any) – The data to serialize.
kwargs (Any) – Passed tojson.dumps().

Return type:

loads(s,**kwargs)¶

Deserialize data as JSON from a string or bytes.

Parameters:

s (str |bytes) – Text or UTF-8 bytes.
kwargs (Any) – Passed tojson.loads().

Return type:

response(*args,**kwargs)¶

Serialize the given arguments as JSON, and return aResponse object with it. The response mimetypewill be “application/json” and can be changed withmimetype.

Ifcompact isFalse or debug mode is enabled, theoutput will be formatted to be easier to read.

Either positional or keyword arguments can be given, not both.If no arguments are given,None is serialized.

Parameters:

args (t.Any) – A single value to serialize, or multiple values totreat as a list to serialize.
kwargs (t.Any) – Treat as a dict to serialize.

Return type:

Tagged JSON¶

A compact representation for lossless serialization of non-standard JSONtypes.SecureCookieSessionInterface uses thisto serialize the session data, but it may be useful in other places. Itcan be extended to support other types.

classflask.json.tag.TaggedJSONSerializer¶

Serializer that uses a tag system to compactly represent objects thatare not JSON types. Passed as the intermediate serializer toitsdangerous.Serializer.

The following extra types are supported:

default_tags=[<class'flask.json.tag.TagDict'>,<class'flask.json.tag.PassDict'>,<class'flask.json.tag.TagTuple'>,<class'flask.json.tag.PassList'>,<class'flask.json.tag.TagBytes'>,<class'flask.json.tag.TagMarkup'>,<class'flask.json.tag.TagUUID'>,<class'flask.json.tag.TagDateTime'>]¶: Tag classes to bind when creating the serializer. Other tags can beadded later usingregister().

register(tag_class,force=False,index=None)¶

Parameters:

tag_class (type[JSONTag]) – tag class to register. Will be instantiated with thisserializer instance.
force (bool) – overwrite an existing tag. If false (default), aKeyError is raised.
index (int |None) – index to insert the new tag in the tag order. Useful whenthe new tag is a special case of an existing tag. IfNone(default), the tag is appended to the end of the order.

Raises:

KeyError – if the tag key is already registered andforce isnot true.

Return type:

None

tag(value)¶

Convert a value to a tagged representation if necessary.

Parameters:: value (Any)
Return type:: Any

untag(value)¶

Convert a tagged representation back to the original type.

Parameters:: value (dict[str,Any])
Return type:: Any

dumps(value)¶

Tag the value and dump it to a compact JSON string.

Parameters:: value (Any)
Return type:: str

loads(value)¶

Load data from a JSON string and deserialized any tagged objects.

Parameters:: value (str)
Return type:: Any

classflask.json.tag.JSONTag(serializer)¶

Base class for defining type tags forTaggedJSONSerializer.

Parameters:: serializer (TaggedJSONSerializer)

key:str=''¶: The tag to mark the serialized object with. If empty, this tag isonly used as an intermediate step during tagging.

check(value)¶

Check if the given value should be tagged by this tag.

Parameters:: value (Any)
Return type:: bool

to_json(value)¶

Convert the Python object to an object that is a valid JSON type.The tag will be added later.

Parameters:: value (Any)
Return type:: Any

to_python(value)¶

Convert the JSON representation back to the correct type. The tagwill already be removed.

Parameters:: value (Any)
Return type:: Any

tag(value)¶

Convert the value to a valid JSON type and add the tag structurearound it.

Parameters:: value (Any)
Return type:: dict[str,Any]

Let’s see an example that adds support forOrderedDict. Dicts don’t have an order in JSON, soto handle this we will dump the items as a list of[key,value]pairs. SubclassJSONTag and give it the new key'od' toidentify the type. The session serializer processes dicts first, soinsert the new tag at the front of the order sinceOrderedDict mustbe processed beforedict.

fromflask.json.tagimportJSONTagclassTagOrderedDict(JSONTag):__slots__=('serializer',)key=' od'defcheck(self,value):returnisinstance(value,OrderedDict)defto_json(self,value):return[[k,self.serializer.tag(v)]fork,viniteritems(value)]defto_python(self,value):returnOrderedDict(value)app.session_interface.serializer.register(TagOrderedDict,index=0)

Template Rendering¶

flask.render_template(template_name_or_list,**context)¶

Render a template by name with the given context.

Parameters:

template_name_or_list (str |Template |list[str |Template]) – The name of the template to render. Ifa list is given, the first name to exist will be rendered.
context (Any) – The variables to make available in the template.

Return type:

flask.render_template_string(source,**context)¶

Render a template from the given source string with the givencontext.

Parameters:

source (str) – The source code of the template to render.
context (Any) – The variables to make available in the template.

Return type:

flask.stream_template(template_name_or_list,**context)¶

Render a template by name with the given context as a stream.This returns an iterator of strings, which can be used as astreaming response from a view.

Parameters:

template_name_or_list (str |Template |list[str |Template]) – The name of the template to render. Ifa list is given, the first name to exist will be rendered.
context (Any) – The variables to make available in the template.

Return type:

Iterator[str]

Changelog

Added in version 2.2.

flask.stream_template_string(source,**context)¶

Render a template from the given source string with the givencontext as a stream. This returns an iterator of strings, which canbe used as a streaming response from a view.

Parameters:

source (str) – The source code of the template to render.
context (Any) – The variables to make available in the template.

Return type:

Iterator[str]

Changelog

Added in version 2.2.

flask.get_template_attribute(template_name,attribute)¶

Loads a macro (or variable) a template exports. This can be used toinvoke a macro from within Python code. If you for example have atemplate named_cider.html with the following contents:

{%macrohello(name)%}Hello{{name}}!{%endmacro%}

You can access this from Python code like this:

hello=get_template_attribute('_cider.html','hello')returnhello('World')

Changelog

Added in version 0.2.

Parameters:

template_name (str) – the name of the template
attribute (str) – the name of the variable of macro to access

Return type:

Configuration¶

classflask.Config(root_path,defaults=None)¶

Works exactly like a dict but provides ways to fill it from filesor special dictionaries. There are two common patterns to populate theconfig.

Either you can fill the config from a config file:

app.config.from_pyfile('yourconfig.cfg')

Or alternatively you can define the configuration options in themodule that callsfrom_object() or provide an import path toa module that should be loaded. It is also possible to tell it touse the same module and with that provide the configuration valuesjust before the call:

DEBUG=TrueSECRET_KEY='development key'app.config.from_object(__name__)

In both cases (loading from any Python file or loading from modules),only uppercase keys are added to the config. This makes it possible to uselowercase values in the config file for temporary values that are not addedto the config or to define the config keys in the same file that implementsthe application.

Probably the most interesting way to load configurations is from anenvironment variable pointing to a file:

app.config.from_envvar('YOURAPPLICATION_SETTINGS')

In this case before launching the application you have to set thisenvironment variable to the file you want to use. On Linux and OS Xuse the export statement:

exportYOURAPPLICATION_SETTINGS='/path/to/config/file'

On windows useset instead.

Parameters:

root_path (str |os.PathLike[str]) – path to which files are read relative from. When theconfig object is created by the application, this isthe application’sroot_path.
defaults (dict[str,t.Any]|None) – an optional dictionary of default values

from_envvar(variable_name,silent=False)¶

Loads a configuration from an environment variable pointing toa configuration file. This is basically just a shortcut with nicererror messages for this line of code:

app.config.from_pyfile(os.environ['YOURAPPLICATION_SETTINGS'])

Parameters:

variable_name (str) – name of the environment variable
silent (bool) – set toTrue if you want silent failure for missingfiles.

Returns:

True if the file was loaded successfully.

Return type:

from_prefixed_env(prefix='FLASK',*,loads=json.loads)¶

Load any environment variables that start withFLASK_,dropping the prefix from the env key for the config key. Valuesare passed through a loading function to attempt to convert themto more specific types than strings.

Keys are loaded insorted() order.

The default loading function attempts to parse values as anyvalid JSON type, including dicts and lists.

Specific items in nested dicts can be set by separating thekeys with double underscores (__). If an intermediate keydoesn’t exist, it will be initialized to an empty dict.

Parameters:

prefix (str) – Load env vars that start with this prefix,separated with an underscore (_).
loads (Callable[[str],Any]) – Pass each string value to this function and usethe returned value as the config value. If any error israised it is ignored and the value remains a string. Thedefault isjson.loads().

Return type:

Changelog

Added in version 2.1.

from_pyfile(filename,silent=False)¶

Updates the values in the config from a Python file. This functionbehaves as if the file was imported as module with thefrom_object() function.

Parameters:

filename (str |PathLike[str]) – the filename of the config. This can either be anabsolute filename or a filename relative to theroot path.
silent (bool) – set toTrue if you want silent failure for missingfiles.

Returns:

True if the file was loaded successfully.

Return type:

Changelog

Added in version 0.7:silent parameter.

from_object(obj)¶

Updates the values from the given object. An object can be of oneof the following two types:

a string: in this case the object with that name will be imported
an actual object reference: that object is used directly

Objects are usually either modules or classes.from_object()loads only the uppercase attributes of the module/class. Adictobject will not work withfrom_object() because the keys of adict are not attributes of thedict class.

Example of module-based configuration:

app.config.from_object('yourapplication.default_config')fromyourapplicationimportdefault_configapp.config.from_object(default_config)

Nothing is done to the object before loading. If the object is aclass and has@property attributes, it needs to beinstantiated before being passed to this method.

You should not use this function to load the actual configuration butrather configuration defaults. The actual config should be loadedwithfrom_pyfile() and ideally from a location not within thepackage because the package might be installed system wide.

SeeDevelopment / Production for an example of class-based configurationusingfrom_object().

Parameters:: obj (object |str) – an import name or object
Return type:: None

from_file(filename,load,silent=False,text=True)¶

Update the values in the config from a file that is loadedusing theload parameter. The loaded data is passed to thefrom_mapping() method.

importjsonapp.config.from_file("config.json",load=json.load)importtomllibapp.config.from_file("config.toml",load=tomllib.load,text=False)

Parameters:

filename (str |PathLike[str]) – The path to the data file. This can be anabsolute path or relative to the config root path.
load (Callable[[Reader],Mapping] whereReaderimplements aread method.) – A callable that takes a file handle and returns amapping of loaded data from the file.
silent (bool) – Ignore the file if it doesn’t exist.
text (bool) – Open the file in text or binary mode.

Returns:

True if the file was loaded successfully.

Return type:

Changelog

Changed in version 2.3:Thetext parameter was added.

Added in version 2.0.

from_mapping(mapping=None,**kwargs)¶

Updates the config likeupdate() ignoring items withnon-upper keys.

Returns:

Always returnsTrue.

Parameters:

mapping (Mapping[str,Any]|None)
kwargs (Any)

Return type:

Changelog

Added in version 0.11.

get_namespace(namespace,lowercase=True,trim_namespace=True)¶

Returns a dictionary containing a subset of configuration optionsthat match the specified namespace/prefix. Example usage:

app.config['IMAGE_STORE_TYPE']='fs'app.config['IMAGE_STORE_PATH']='/var/app/images'app.config['IMAGE_STORE_BASE_URL']='http://img.website.com'image_store_config=app.config.get_namespace('IMAGE_STORE_')

The resulting dictionaryimage_store_config would look like:

{'type':'fs','path':'/var/app/images','base_url':'http://img.website.com'}

This is often useful when configuration options map directly tokeyword arguments in functions or class constructors.

Parameters:

namespace (str) – a configuration namespace
lowercase (bool) – a flag indicating if the keys of the resultingdictionary should be lowercase
trim_namespace (bool) – a flag indicating if the keys of the resultingdictionary should not include the namespace

Return type:

dict[str,Any]

Changelog

Added in version 0.11.

Stream Helpers¶

flask.stream_with_context(generator_or_function:Iterator)→Iterator¶

flask.stream_with_context(generator_or_function:Callable[[...],Iterator])→Callable[[Iterator],Iterator]

Wrap a response generator function so that it runs inside the currentrequest context. This keepsrequest,session, andgavailable, even though at the point the generator runs the request contextwill typically have ended.

Use it as a decorator on a generator function:

fromflaskimportstream_with_context,request,Response@app.get("/stream")defstreamed_response():@stream_with_contextdefgenerate():yield"Hello "yieldrequest.args["name"]yield"!"returnResponse(generate())

Or use it as a wrapper around a created generator:

fromflaskimportstream_with_context,request,Response@app.get("/stream")defstreamed_response():defgenerate():yield"Hello "yieldrequest.args["name"]yield"!"returnResponse(stream_with_context(generate()))

Changelog

Added in version 0.9.

Useful Internals¶

classflask.ctx.RequestContext(app,environ,request=None,session=None)¶

The request context contains per-request information. The Flaskapp creates and pushes it at the beginning of the request, then popsit at the end of the request. It will create the URL adapter andrequest object for the WSGI environment provided.

Do not attempt to use this class directly, instead usetest_request_context() andrequest_context() to create this object.

When the request context is popped, it will evaluate all thefunctions registered on the application for teardown execution(teardown_request()).

The request context is automatically popped at the end of therequest. When using the interactive debugger, the context will berestored sorequest is still accessible. Similarly, the testclient can preserve the context after the request ends. However,teardown functions may already have closed some resources such asdatabase connections.

Parameters:

app (Flask)
environ (WSGIEnvironment)
request (Request |None)
session (SessionMixin |None)

copy()¶

Creates a copy of this request context with the same request object.This can be used to move a request context to a different greenlet.Because the actual request object is the same this cannot be used tomove a request context to a different thread unless access to therequest object is locked.

Changelog

Changed in version 1.1:The current session object is used instead of reloading the originaldata. This preventsflask.session pointing to an out-of-date object.

Added in version 0.10.

Return type:: RequestContext

match_request()¶

Can be overridden by a subclass to hook into the matchingof the request.

Return type:: None

pop(exc=_sentinel)¶

Pops the request context and unbinds it by doing that. This willalso trigger the execution of functions registered by theteardown_request() decorator.

Changelog

Changed in version 0.9:Added theexc argument.

Parameters:: exc (BaseException |None)
Return type:: None

flask.globals.request_ctx¶

The currentRequestContext. If a request contextis not active, accessing attributes on this proxy will raise aRuntimeError.

This is an internal object that is essential to how Flask handlesrequests. Accessing this should not be needed in most cases. Mostlikely you wantrequest andsession instead.

classflask.ctx.AppContext(app)¶

The app context contains application-specific information. An appcontext is created and pushed at the beginning of each request ifone is not already active. An app context is also pushed whenrunning CLI commands.

Parameters:: app (Flask)

push()¶

Binds the app context to the current context.

Return type:: None

pop(exc=_sentinel)¶

Pops the app context.

Parameters:: exc (BaseException |None)
Return type:: None

flask.globals.app_ctx¶

The currentAppContext. If an app context is notactive, accessing attributes on this proxy will raise aRuntimeError.

This is an internal object that is essential to how Flask handlesrequests. Accessing this should not be needed in most cases. Mostlikely you wantcurrent_app andg instead.

classflask.blueprints.BlueprintSetupState(blueprint,app,options,first_registration)¶

Temporary holder object for registering a blueprint with theapplication. An instance of this class is created by themake_setup_state() method and later passedto all register callback functions.

Parameters:

blueprint (Blueprint)
app (App)
options (t.Any)
first_registration (bool)

app¶: a reference to the current application

blueprint¶: a reference to the blueprint that created this setup state.

options¶: a dictionary with all options that were passed to theregister_blueprint() method.

first_registration¶: as blueprints can be registered multiple times with theapplication and not everything wants to be registeredmultiple times on it, this attribute can be used to figureout if the blueprint was registered in the past already.

subdomain¶: The subdomain that the blueprint should be active for,Noneotherwise.

url_prefix¶: The prefix that should be used for all URLs defined on theblueprint.

url_defaults¶: A dictionary with URL defaults that is added to each and everyURL that was defined with the blueprint.

add_url_rule(rule,endpoint=None,view_func=None,**options)¶

A helper method to register a rule (and optionally a view function)to the application. The endpoint is automatically prefixed with theblueprint’s name.

Parameters:

rule (str)
endpoint (str |None)
view_func (ft.RouteCallable |None)
options (t.Any)

Return type:

None

Signals¶

Signals are provided by theBlinker library. SeeSignals for an introduction.

flask.template_rendered¶

This signal is sent when a template was successfully rendered. Thesignal is invoked with the instance of the template astemplateand the context as dictionary (namedcontext).

Example subscriber:

deflog_template_renders(sender,template,context,**extra):sender.logger.debug('Rendering template "%s" with context%s',template.nameor'string template',context)fromflaskimporttemplate_renderedtemplate_rendered.connect(log_template_renders,app)

flask.before_render_template

This signal is sent before template rendering process. Thesignal is invoked with the instance of the template astemplateand the context as dictionary (namedcontext).

Example subscriber:

deflog_template_renders(sender,template,context,**extra):sender.logger.debug('Rendering template "%s" with context%s',template.nameor'string template',context)fromflaskimportbefore_render_templatebefore_render_template.connect(log_template_renders,app)

flask.request_started¶

This signal is sent when the request context is set up, beforeany request processing happens. Because the request context is alreadybound, the subscriber can access the request with the standard globalproxies such asrequest.

Example subscriber:

deflog_request(sender,**extra):sender.logger.debug('Request context is set up')fromflaskimportrequest_startedrequest_started.connect(log_request,app)

flask.request_finished¶

This signal is sent right before the response is sent to the client.It is passed the response to be sent namedresponse.

Example subscriber:

deflog_response(sender,response,**extra):sender.logger.debug('Request context is about to close down. ''Response:%s',response)fromflaskimportrequest_finishedrequest_finished.connect(log_response,app)

flask.got_request_exception¶

This signal is sent when an unhandled exception happens duringrequest processing, including when debugging. The exception ispassed to the subscriber asexception.

This signal is not sent forHTTPException, or other exceptions thathave error handlers registered, unless the exception was raised froman error handler.

This example shows how to do some extra logging if a theoreticalSecurityException was raised:

fromflaskimportgot_request_exceptiondeflog_security_exception(sender,exception,**extra):ifnotisinstance(exception,SecurityException):returnsecurity_logger.exception(f"SecurityException at{request.url!r}",exc_info=exception,)got_request_exception.connect(log_security_exception,app)

flask.request_tearing_down¶

This signal is sent when the request is tearing down. This is alwayscalled, even if an exception is caused. Currently functions listeningto this signal are called after the regular teardown handlers, but thisis not something you can rely on.

Example subscriber:

defclose_db_connection(sender,**extra):session.close()fromflaskimportrequest_tearing_downrequest_tearing_down.connect(close_db_connection,app)

As of Flask 0.9, this will also be passed anexc keyword argumentthat has a reference to the exception that caused the teardown ifthere was one.

flask.appcontext_tearing_down¶

This signal is sent when the app context is tearing down. This is alwayscalled, even if an exception is caused. Currently functions listeningto this signal are called after the regular teardown handlers, but thisis not something you can rely on.

Example subscriber:

defclose_db_connection(sender,**extra):session.close()fromflaskimportappcontext_tearing_downappcontext_tearing_down.connect(close_db_connection,app)

This will also be passed anexc keyword argument that has a referenceto the exception that caused the teardown if there was one.

flask.appcontext_pushed¶

This signal is sent when an application context is pushed. The senderis the application. This is usually useful for unittests in order totemporarily hook in information. For instance it can be used toset a resource early onto theg object.

Example usage:

fromcontextlibimportcontextmanagerfromflaskimportappcontext_pushed@contextmanagerdefuser_set(app,user):defhandler(sender,**kwargs):g.user=userwithappcontext_pushed.connected_to(handler,app):yield

And in the testcode:

deftest_user_me(self):withuser_set(app,'john'):c=app.test_client()resp=c.get('/users/me')assertresp.data=='username=john'

Changelog

Added in version 0.10.

flask.appcontext_popped¶: This signal is sent when an application context is popped. The senderis the application. This usually falls in line with theappcontext_tearing_down signal.
Changelog
Added in version 0.10.

flask.message_flashed¶

This signal is sent when the application is flashing a message. Themessages is sent asmessage keyword argument and the category ascategory.

Example subscriber:

recorded=[]defrecord(sender,message,category,**extra):recorded.append((message,category))fromflaskimportmessage_flashedmessage_flashed.connect(record,app)

Changelog

Added in version 0.10.

Class-Based Views¶

Changelog

Added in version 0.7.

classflask.views.View¶

Subclass this class and overridedispatch_request() tocreate a generic class-based view. Callas_view() to create aview function that creates an instance of the class with the givenarguments and calls itsdispatch_request method with any URLvariables.

SeeClass-based Views for a detailed guide.

classHello(View):init_every_request=Falsedefdispatch_request(self,name):returnf"Hello,{name}!"app.add_url_rule("/hello/<name>",view_func=Hello.as_view("hello"))

Setmethods on the class to change what methods the viewaccepts.

Setdecorators on the class to apply a list of decorators tothe generated view function. Decorators applied to the class itselfwill not be applied to the generated view function!

Setinit_every_request toFalse for efficiency, unlessyou need to store request-global data onself.

methods:ClassVar[Collection[str]|None]=None¶: The methods this view is registered for. Uses the same default(["GET","HEAD","OPTIONS"]) asroute andadd_url_rule by default.

provide_automatic_options:ClassVar[bool|None]=None¶: Control whether theOPTIONS method is handled automatically.Uses the same default (True) asroute andadd_url_rule by default.

decorators:ClassVar[list[Callable[[...],Any]]]=[]¶: A list of decorators to apply, in order, to the generated viewfunction. Remember that@decorator syntax is applied bottomto top, so the first decorator in the list would be the bottomdecorator.
Changelog
Added in version 0.8.

init_every_request:ClassVar[bool]=True¶

Create a new instance of this view class for every request bydefault. If a view subclass sets this toFalse, the sameinstance is used for every request.

A single instance is more efficient, especially if complex setupis done during init. However, storing data onself is nolonger safe across requests, andg should be usedinstead.

Changelog

Added in version 2.2.

dispatch_request()¶

The actual view function behavior. Subclasses must overridethis and return a valid response. Any variables from the URLrule are passed as keyword arguments.

Return type:: ft.ResponseReturnValue

classmethodas_view(name,*class_args,**class_kwargs)¶

Convert the class into a view function that can be registeredfor a route.

By default, the generated view will create a new instance of theview class for every request and call itsdispatch_request() method. If the view class setsinit_every_request toFalse, the same instance willbe used for every request.

Except forname, all other arguments passed to this methodare forwarded to the view class__init__ method.

Changelog

Changed in version 2.2:Added theinit_every_request class attribute.

Parameters:

name (str)
class_args (t.Any)
class_kwargs (t.Any)

Return type:

ft.RouteCallable

classflask.views.MethodView¶

Dispatches request methods to the corresponding instance methods.For example, if you implement aget method, it will be used tohandleGET requests.

This can be useful for defining a REST API.

methods is automatically set based on the methods defined onthe class.

SeeClass-based Views for a detailed guide.

classCounterAPI(MethodView):defget(self):returnstr(session.get("counter",0))defpost(self):session["counter"]=session.get("counter",0)+1returnredirect(url_for("counter"))app.add_url_rule("/counter",view_func=CounterAPI.as_view("counter"))

dispatch_request(**kwargs)¶

The actual view function behavior. Subclasses must overridethis and return a valid response. Any variables from the URLrule are passed as keyword arguments.

Parameters:: kwargs (t.Any)
Return type:: ft.ResponseReturnValue

URL Route Registrations¶

Generally there are three ways to define rules for the routing system:

You can use theflask.Flask.route() decorator.
You can use theflask.Flask.add_url_rule() function.
You can directly access the underlying Werkzeug routing systemwhich is exposed asflask.Flask.url_map.

Variable parts in the route can be specified with angular brackets(/user/<username>). By default a variable part in the URL accepts anystring without a slash however a different converter can be specified aswell by using<converter:name>.

Variable parts are passed to the view function as keyword arguments.

The following converters are available:

`string`	accepts any text without a slash (the default)
`int`	accepts integers
`float`	like`int` but for floating point values
`path`	like the default but also accepts slashes
`any`	matches one of the items provided
`uuid`	accepts UUID strings

Custom converters can be defined usingflask.Flask.url_map.

Here are some examples:

@app.route('/')defindex():pass@app.route('/<username>')defshow_user(username):pass@app.route('/post/<int:post_id>')defshow_post(post_id):pass

An important detail to keep in mind is how Flask deals with trailingslashes. The idea is to keep each URL unique so the following rulesapply:

If a rule ends with a slash and is requested without a slash by theuser, the user is automatically redirected to the same page with atrailing slash attached.
If a rule does not end with a trailing slash and the user requests thepage with a trailing slash, a 404 not found is raised.

This is consistent with how web servers deal with static files. Thisalso makes it possible to use relative link targets safely.

You can also define multiple rules for the same function. They have to beunique however. Defaults can also be specified. Here for example is adefinition for a URL that accepts an optional page:

@app.route('/users/',defaults={'page':1})@app.route('/users/page/<int:page>')defshow_users(page):pass

This specifies that/users/ will be the URL for page one and/users/page/N will be the URL for pageN.

If a URL contains a default value, it will be redirected to its simplerform with a 301 redirect. In the above example,/users/page/1 willbe redirected to/users/. If your route handlesGET andPOSTrequests, make sure the default route only handlesGET, as redirectscan’t preserve form data.

@app.route('/region/',defaults={'id':1})@app.route('/region/<int:id>',methods=['GET','POST'])defregion(id):pass

Here are the parameters thatroute() andadd_url_rule() accept. The only difference is thatwith the route parameter the view function is defined with the decoratorinstead of theview_func parameter.

`rule`	the URL rule as string
`endpoint`	the endpoint for the registered URL rule. Flask itselfassumes that the name of the view function is the nameof the endpoint if not explicitly stated.
`view_func`	the function to call when serving a request to theprovided endpoint. If this is not provided one canspecify the function later by storing it in the`view_functions` dictionary with theendpoint as key.
`defaults`	A dictionary with defaults for this rule. See theexample above for how defaults work.
`subdomain`	specifies the rule for the subdomain in case subdomainmatching is in use. If not specified the defaultsubdomain is assumed.
`**options`	the options to be forwarded to the underlying`Rule` object. A change toWerkzeug is handling of method options. methods is a listof methods this rule should be limited to (`GET`,`POST`etc.). By default a rule just listens for`GET` (andimplicitly`HEAD`). Starting with Flask 0.6,`OPTIONS` isimplicitly added and handled by the standard requesthandling. They have to be specified as keyword arguments.

View Function Options¶

For internal usage the view functions can have some attributes attached tocustomize behavior the view function would normally not have control over.The following attributes can be provided optionally to either overridesome defaults toadd_url_rule() or general behavior:

__name__: The name of a function is by default used as endpoint. Ifendpoint is provided explicitly this value is used. Additionally thiswill be prefixed with the name of the blueprint by default whichcannot be customized from the function itself.
methods: If methods are not provided when the URL rule is added,Flask will look on the view function object itself if amethodsattribute exists. If it does, it will pull the information for themethods from there.
provide_automatic_options: if this attribute is set Flask willeither force enable or disable the automatic implementation of theHTTPOPTIONS response. This can be useful when working withdecorators that want to customize theOPTIONS response on a per-viewbasis.
required_methods: if this attribute is set, Flask will always addthese methods when registering a URL rule even if the methods wereexplicitly overridden in theroute() call.

Full example:

defindex():ifrequest.method=='OPTIONS':# custom options handling here...return'Hello World!'index.provide_automatic_options=Falseindex.methods=['GET','OPTIONS']app.add_url_rule('/',index)

Changelog

Added in version 0.8:Theprovide_automatic_options functionality was added.

Command Line Interface¶

classflask.cli.FlaskGroup(add_default_commands=True,create_app=None,add_version_option=True,load_dotenv=True,set_debug_flag=True,**extra)¶

Special subclass of theAppGroup group that supportsloading more commands from the configured Flask app. Normally adeveloper does not have to interface with this class but there aresome very advanced use cases for which it makes sense to create aninstance of this. seeCustom Scripts.

Parameters:

add_default_commands (bool) – if this is True then the default run andshell commands will be added.
add_version_option (bool) – adds the--version option.
create_app (t.Callable[...,Flask]|None) – an optional callback that is passed the script info andreturns the loaded app.
load_dotenv (bool) – Load the nearest.env and.flaskenvfiles to set environment variables. Will also change the workingdirectory to the directory containing the first file found.
set_debug_flag (bool) – Set the app’s debug flag.
extra (t.Any)

Changed in version 3.1:-epath takes precedence over default.env and.flaskenv files.

Changelog

Changed in version 2.2:Added the-A/--app,--debug/--no-debug,-e/--env-file options.

Changed in version 2.2:An app context is pushed when runningapp.cli commands, so@with_appcontext is no longer required for those commands.

Changed in version 1.0:If installed, python-dotenv will be used to load environment variablesfrom.env and.flaskenv files.

get_command(ctx,name)¶

Given a context and a command name, this returns aCommandobject if it exists or returnsNone.

Parameters:

ctx (Context)
name (str)

Return type:

Command | None

list_commands(ctx)¶

Returns a list of subcommand names in the order they should appear.

Parameters:: ctx (Context)
Return type:: list[str]

make_context(info_name,args,parent=None,**extra)¶

This function when given an info name and arguments will kickoff the parsing and create a newContext. It does notinvoke the actual command callback though.

To quickly customize the context class used without overridingthis method, set thecontext_class attribute.

Parameters:

info_name (str |None) – the info name for this invocation. Generally thisis the most descriptive name for the script orcommand. For the toplevel script it’s usuallythe name of the script, for commands below it’sthe name of the command.
args (list[str]) – the arguments to parse as list of strings.
parent (Context |None) – the parent context if available.
extra (Any) – extra keyword arguments forwarded to the contextconstructor.

Return type:

Context

Changed in version 8.0:Added thecontext_class attribute.

classflask.cli.AppGroup(name=None,commands=None,invoke_without_command=False,no_args_is_help=None,subcommand_metavar=None,chain=False,result_callback=None,**kwargs)¶

This works similar to a regular clickGroup but itchanges the behavior of thecommand() decorator so that itautomatically wraps the functions inwith_appcontext().

Not to be confused withFlaskGroup.

Parameters:

name (str |None)
commands (cabc.MutableMapping[str,Command]|cabc.Sequence[Command]|None)
invoke_without_command (bool)
no_args_is_help (bool |None)
subcommand_metavar (str |None)
chain (bool)
result_callback (t.Callable[...,t.Any]|None)
kwargs (t.Any)

command(*args,**kwargs)¶

This works exactly like the method of the same name on a regularclick.Group but it wraps callbacks inwith_appcontext()unless it’s disabled by passingwith_appcontext=False.

Parameters:

args (Any)
kwargs (Any)

Return type:

Callable[[Callable[[…],Any]],Command]

group(*args,**kwargs)¶

This works exactly like the method of the same name on a regularclick.Group but it defaults the group class toAppGroup.

Parameters:

args (Any)
kwargs (Any)

Return type:

Callable[[Callable[[…],Any]],Group]

classflask.cli.ScriptInfo(app_import_path=None,create_app=None,set_debug_flag=True,load_dotenv_defaults=True)¶

Helper object to deal with Flask applications. This is usually notnecessary to interface with as it’s used internally in the dispatchingto click. In future versions of Flask this object will most likely playa bigger role. Typically it’s created automatically by theFlaskGroup but you can also manually create it and pass itonwards as click object.

Changed in version 3.1:Added theload_dotenv_defaults parameter and attribute.

Parameters:

app_import_path (str |None)
create_app (t.Callable[...,Flask]|None)
set_debug_flag (bool)
load_dotenv_defaults (bool)

app_import_path¶: Optionally the import path for the Flask application.

create_app¶: Optionally a function that is passed the script info to createthe instance of the application.

data:dict[t.Any,t.Any]¶: A dictionary with arbitrary data that can be associated withthis script info.

load_dotenv_defaults¶

Whether default.flaskenv and.env files should be loaded.

ScriptInfo doesn’t load anything, this is for reference when doingthe load elsewhere during processing.

Added in version 3.1.

load_app()¶

Loads the Flask app (if not yet loaded) and returns it. Callingthis multiple times will just result in the already loaded app tobe returned.

Return type:: Flask

flask.cli.load_dotenv(path=None,load_defaults=True)¶

Load “dotenv” files to set environment variables. A given path takesprecedence over.env, which takes precedence over.flaskenv. Afterloading and combining these files, values are only set if the key is notalready set inos.environ.

This is a no-op ifpython-dotenv is not installed.

Parameters:

path (str |PathLike[str]|None) – Load the file at this location.
load_defaults (bool) – Search for and load the default.flaskenv and.env files.

Returns:

True if at least one env var was loaded.

Return type: