New in version 3.1.

31.5.1. Introduction¶

The purpose of theimportlib package is two-fold. One is to provide theimplementation of theimport statement (and thus, by extension, the__import__() function) in Python source code. This provides animplementation ofimport which is portable to any Pythoninterpreter. This also provides an implementation which is easier tocomprehend than one implemented in a programming language other than Python.

Two, the components to implementimport are exposed in thispackage, making it easier for users to create their own custom objects (knowngenerically as animporter) to participate in the import process.

31.5.2. Functions¶

importlib.__import__(name,globals=None,locals=None,fromlist=(),level=0)¶

An implementation of the built-in__import__() function.

Note

Programmatic importing of modules should useimport_module()instead of this function.

importlib.import_module(name,package=None)¶

Import a module. Thename argument specifies what module toimport in absolute or relative terms(e.g. eitherpkg.mod or..mod). If the name isspecified in relative terms, then thepackage argument must be set tothe name of the package which is to act as the anchor for resolving thepackage name (e.g.import_module('..mod','pkg.subpkg') will importpkg.mod).

Theimport_module() function acts as a simplifying wrapper aroundimportlib.__import__(). This means all semantics of the function arederived fromimportlib.__import__(). The most important differencebetween these two functions is thatimport_module() returns thespecified package or module (e.g.pkg.mod), while__import__()returns the top-level package or module (e.g.pkg).

If you are dynamically importing a module that was created since theinterpreter began execution (e.g., created a Python source file), you mayneed to callinvalidate_caches() in order for the new module to benoticed by the import system.

Changed in version 3.3:Parent packages are automatically imported.

importlib.find_loader(name,path=None)¶

Find the loader for a module, optionally within the specifiedpath. If themodule is insys.modules, thensys.modules[name].__loader__ isreturned (unless the loader would beNone or is not set, in which caseValueError is raised). Otherwise a search usingsys.meta_pathis done.None is returned if no loader is found.

A dotted name does not have its parents implicitly imported as that requiresloading them and that may not be desired. To properly import a submodule youwill need to import all parent packages of the submodule and use the correctargument topath.

New in version 3.3.

Changed in version 3.4:If__loader__ is not set, raiseValueError, just like when theattribute is set toNone.

Deprecated since version 3.4:Useimportlib.util.find_spec() instead.

importlib.invalidate_caches()¶

Invalidate the internal caches of finders stored atsys.meta_path. If a finder implementsinvalidate_caches() then itwill be called to perform the invalidation. This function should be calledif any modules are created/installed while your program is running toguarantee all finders will notice the new module’s existence.

New in version 3.3.

importlib.reload(module)¶

Reload a previously importedmodule. The argument must be a module object,so it must have been successfully imported before. This is useful if youhave edited the module source file using an external editor and want to tryout the new version without leaving the Python interpreter. The return valueis the module object (which can be different if re-importing causes adifferent object to be placed insys.modules).

Whenreload() is executed:

• Python module’s code is recompiled and the module-level code re-executed,defining a new set of objects which are bound to names in the module’sdictionary by reusing theloader which originally loaded themodule. Theinit function of extension modules is not called a secondtime.
• As with all other objects in Python the old objects are only reclaimedafter their reference counts drop to zero.
• The names in the module namespace are updated to point to any new orchanged objects.
• Other references to the old objects (such as names external to the module) arenot rebound to refer to the new objects and must be updated in each namespacewhere they occur if that is desired.

There are a number of other caveats:

When a module is reloaded, its dictionary (containing the module’s globalvariables) is retained. Redefinitions of names will override the olddefinitions, so this is generally not a problem. If the new version of amodule does not define a name that was defined by the old version, the olddefinition remains. This feature can be used to the module’s advantage if itmaintains a global table or cache of objects — with atrystatement it can test for the table’s presence and skip its initialization ifdesired:

try:cacheexceptNameError:cache={}

It is generally not very useful to reload built-in or dynamically loadedmodules. Reloadingsys,__main__,builtins and otherkey modules is not recommended. In many cases extension modules are notdesigned to be initialized more than once, and may fail in arbitrary wayswhen reloaded.

If a module imports objects from another module usingfrom …import …, callingreload() for the other module does notredefine the objects imported from it — one way around this is tore-execute thefrom statement, another is to useimportand qualified names (module.name) instead.

If a module instantiates instances of a class, reloading the module thatdefines the class does not affect the method definitions of the instances —they continue to use the old class definition. The same is true for derivedclasses.

New in version 3.4.

31.5.3.importlib.abc – Abstract base classes related to import¶

Source code:Lib/importlib/abc.py

Theimportlib.abc module contains all of the core abstract base classesused byimport. Some subclasses of the core abstract base classesare also provided to help in implementing the core ABCs.

ABC hierarchy:

object+--Finder(deprecated)|+--MetaPathFinder|+--PathEntryFinder+--Loader+--ResourceLoader--------++--InspectLoader|+--ExecutionLoader--++--FileLoader+--SourceLoader

classimportlib.abc.Finder¶

An abstract base class representing afinder.

Deprecated since version 3.3:UseMetaPathFinder orPathEntryFinder instead.

abstractmethodfind_module(fullname,path=None)¶

An abstact method for finding aloader for the specifiedmodule. Originally specified inPEP 302, this method was meantfor use insys.meta_path and in the path-based import subsystem.

Changed in version 3.4:ReturnsNone when called instead of raisingNotImplementedError.

classimportlib.abc.MetaPathFinder¶

An abstract base class representing ameta path finder. Forcompatibility, this is a subclass ofFinder.

New in version 3.3.

find_spec(fullname,path,target=None)¶

An abstract method for finding aspec forthe specified module. If this is a top-level import,path willbeNone. Otherwise, this is a search for a subpackage ormodule andpath will be the value of__path__ from theparent package. If a spec cannot be found,None is returned.When passed in,target is a module object that the finder mayuse to make a more educated about what spec to return.

New in version 3.4.

find_module(fullname,path)¶

A legacy method for finding aloader for the specifiedmodule. If this is a top-level import,path will beNone.Otherwise, this is a search for a subpackage or module andpathwill be the value of__path__ from the parentpackage. If a loader cannot be found,None is returned.

Iffind_spec() is defined, backwards-compatible functionality isprovided.

Changed in version 3.4:ReturnsNone when called instead of raisingNotImplementedError. Can usefind_spec() to providefunctionality.

Deprecated since version 3.4:Usefind_spec() instead.

invalidate_caches()¶

An optional method which, when called, should invalidate any internalcache used by the finder. Used byimportlib.invalidate_caches()when invalidating the caches of all finders onsys.meta_path.

Changed in version 3.4:ReturnsNone when called instead ofNotImplemented.

classimportlib.abc.PathEntryFinder¶

An abstract base class representing apath entry finder. Thoughit bears some similarities toMetaPathFinder,PathEntryFinderis meant for use only within the path-based import subsystem providedbyPathFinder. This ABC is a subclass ofFinder forcompatibility reasons only.

New in version 3.3.

find_spec(fullname,target=None)¶

An abstract method for finding aspec forthe specified module. The finder will search for the module onlywithin thepath entry to which it is assigned. If a speccannot be found,None is returned. When passed in,targetis a module object that the finder may use to make a more educatedabout what spec to return.

New in version 3.4.

find_loader(fullname)¶

A legacy method for finding aloader for the specifiedmodule. Returns a 2-tuple of(loader,portion) whereportionis a sequence of file system locations contributing to part of a namespacepackage. The loader may beNone while specifyingportion tosignify the contribution of the file system locations to a namespacepackage. An empty list can be used forportion to signify the loaderis not part of a namespace package. Ifloader isNone andportion is the empty list then no loader or location for a namespacepackage were found (i.e. failure to find anything for the module).

Iffind_spec() is defined then backwards-compatible functionality isprovided.

Changed in version 3.4:Returns(None,[]) instead of raisingNotImplementedError.Usesfind_spec() when available to provide functionality.

Deprecated since version 3.4:Usefind_spec() instead.

find_module(fullname)¶

A concrete implementation ofFinder.find_module() which isequivalent toself.find_loader(fullname)[0].

Deprecated since version 3.4:Usefind_spec() instead.

invalidate_caches()¶

An optional method which, when called, should invalidate any internalcache used by the finder. Used byPathFinder.invalidate_caches()when invalidating the caches of all cached finders.

classimportlib.abc.Loader¶

An abstract base class for aloader.SeePEP 302 for the exact definition for a loader.

create_module(spec)¶

A method that returns the module object to use whenimporting a module. This method may returnNone,indicating that default module creation semantics should take place.

New in version 3.4.

Changed in version 3.5:Starting in Python 3.6, this method will not be optional whenexec_module() is defined.

exec_module(module)¶

An abstract method that executes the module in its own namespacewhen a module is imported or reloaded. The module should alreadybe initialized when exec_module() is called.

New in version 3.4.

load_module(fullname)¶

A legacy method for loading a module. If the module cannot beloaded,ImportError is raised, otherwise the loaded module isreturned.

If the requested module already exists insys.modules, thatmodule should be used and reloaded.Otherwise the loader should create a new module and insert it intosys.modules before any loading begins, to prevent recursionfrom the import. If the loader inserted a module and the load fails, itmust be removed by the loader fromsys.modules; modules alreadyinsys.modules before the loader began execution should be leftalone (seeimportlib.util.module_for_loader()).

The loader should set several attributes on the module.(Note that some of these attributes can change when a module isreloaded):

• __name__

  The name of the module.

• __file__

  The path to where the module data is stored (not set for built-inmodules).

• __cached__

  The path to where a compiled version of the module is/should bestored (not set when the attribute would be inappropriate).

• __path__

  A list of strings specifying the search path within apackage. This attribute is not set on modules.

• __package__

  The parent package for the module/package. If the module istop-level then it has a value of the empty string. Theimportlib.util.module_for_loader() decorator can handle thedetails for__package__.

• __loader__

  The loader used to load the module. Theimportlib.util.module_for_loader() decorator can handle thedetails for__package__.

Whenexec_module() is available then backwards-compatiblefunctionality is provided.

Changed in version 3.4:RaiseImportError when called instead ofNotImplementedError. Functionality provided whenexec_module() is available.

Deprecated since version 3.4:The recommended API for loading a module isexec_module()(andcreate_module()). Loaders should implementit instead of load_module(). The import machinery takes care ofall the other responsibilities of load_module() when exec_module()is implemented.

module_repr(module)¶

A legacy method which when implemented calculates and returns thegiven module’s repr, as a string. The module type’s default repr() willuse the result of this method as appropriate.

New in version 3.3.

Changed in version 3.4:Made optional instead of an abstractmethod.

Deprecated since version 3.4:The import machinery now takes care of this automatically.

classimportlib.abc.ResourceLoader¶

An abstract base class for aloader which implements the optionalPEP 302 protocol for loading arbitrary resources from the storageback-end.

abstractmethodget_data(path)¶

An abstract method to return the bytes for the data located atpath.Loaders that have a file-like storage back-endthat allows storing arbitrary datacan implement this abstract method to give direct accessto the data stored.OSError is to be raised if thepath cannotbe found. Thepath is expected to be constructed using a module’s__file__ attribute or an item from a package’s__path__.

Changed in version 3.4:RaisesOSError instead ofNotImplementedError.

classimportlib.abc.InspectLoader¶

An abstract base class for aloader which implements the optionalPEP 302 protocol for loaders that inspect modules.

get_code(fullname)¶

Return the code object for a module, orNone if the module does nothave a code object (as would be the case, for example, for a built-inmodule). Raise anImportError if loader cannot find therequested module.

Note

While the method has a default implementation, it is suggested thatit be overridden if possible for performance.

Changed in version 3.4:No longer abstract and a concrete implementation is provided.

abstractmethodget_source(fullname)¶

An abstract method to return the source of a module. It is returned asa text string usinguniversal newlines, translating allrecognized line separators into'\n' characters. ReturnsNoneif no source is available (e.g. a built-in module). RaisesImportError if the loader cannot find the module specified.

Changed in version 3.4:RaisesImportError instead ofNotImplementedError.

is_package(fullname)¶

An abstract method to return a true value if the module is a package, afalse value otherwise.ImportError is raised if theloader cannot find the module.

Changed in version 3.4:RaisesImportError instead ofNotImplementedError.

staticsource_to_code(data,path='<string>')¶

Create a code object from Python source.

Thedata argument can be whatever thecompile() functionsupports (i.e. string or bytes). Thepath argument should bethe “path” to where the source code originated from, which can be anabstract concept (e.g. location in a zip file).

With the subsequent code object one can execute it in a module byrunningexec(code,module.__dict__).

New in version 3.4.

Changed in version 3.5:Made the method static.

exec_module(module)¶

Implementation ofLoader.exec_module().

New in version 3.4.

load_module(fullname)¶

Implementation ofLoader.load_module().

Deprecated since version 3.4:useexec_module() instead.

classimportlib.abc.ExecutionLoader¶

An abstract base class which inherits fromInspectLoader that,when implemented, helps a module to be executed as a script. The ABCrepresents an optionalPEP 302 protocol.

abstractmethodget_filename(fullname)¶

An abstract method that is to return the value of__file__ forthe specified module. If no path is available,ImportError israised.

If source code is available, then the method should return the path tothe source file, regardless of whether a bytecode was used to load themodule.

Changed in version 3.4:RaisesImportError instead ofNotImplementedError.

classimportlib.abc.FileLoader(fullname,path)¶

An abstract base class which inherits fromResourceLoader andExecutionLoader, providing concrete implementations ofResourceLoader.get_data() andExecutionLoader.get_filename().

Thefullname argument is a fully resolved name of the module the loader isto handle. Thepath argument is the path to the file for the module.

New in version 3.3.

name¶

The name of the module the loader can handle.

path¶

Path to the file of the module.

load_module(fullname)¶

Calls super’sload_module().

Deprecated since version 3.4:UseLoader.exec_module() instead.

abstractmethodget_filename(fullname)¶

Returnspath.

abstractmethodget_data(path)¶

Readspath as a binary file and returns the bytes from it.

classimportlib.abc.SourceLoader¶

An abstract base class for implementing source (and optionally bytecode)file loading. The class inherits from bothResourceLoader andExecutionLoader, requiring the implementation of:

• ResourceLoader.get_data()

• ExecutionLoader.get_filename()

  Should only return the path to the source file; sourcelessloading is not supported.

The abstract methods defined by this class are to add optional bytecodefile support. Not implementing these optional methods (or causing them toraiseNotImplementedError) causes the loader toonly work with source code. Implementing the methods allows the loader towork with sourceand bytecode files; it does not allow forsourcelessloading where only bytecode is provided. Bytecode files are anoptimization to speed up loading by removing the parsing step of Python’scompiler, and so no bytecode-specific API is exposed.

path_stats(path)¶

Optional abstract method which returns adict containingmetadata about the specified path. Supported dictionary keys are:

• 'mtime' (mandatory): an integer or floating-point numberrepresenting the modification time of the source code;
• 'size' (optional): the size in bytes of the source code.

Any other keys in the dictionary are ignored, to allow for futureextensions. If the path cannot be handled,OSError is raised.

New in version 3.3.

Changed in version 3.4:RaiseOSError instead ofNotImplementedError.

path_mtime(path)¶

Optional abstract method which returns the modification time for thespecified path.

Deprecated since version 3.3:This method is deprecated in favour ofpath_stats(). You don’thave to implement it, but it is still available for compatibilitypurposes. RaiseOSError if the path cannot be handled.

Changed in version 3.4:RaiseOSError instead ofNotImplementedError.

set_data(path,data)¶

Optional abstract method which writes the specified bytes to a filepath. Any intermediate directories which do not exist are to be createdautomatically.

When writing to the path fails because the path is read-only(errno.EACCES/PermissionError), do not propagate theexception.

Changed in version 3.4:No longer raisesNotImplementedError when called.

get_code(fullname)¶

Concrete implementation ofInspectLoader.get_code().

exec_module(module)¶

Concrete implementation ofLoader.exec_module().

New in version 3.4.

load_module(fullname)¶

Concrete implementation ofLoader.load_module().

Deprecated since version 3.4:Useexec_module() instead.

get_source(fullname)¶

Concrete implementation ofInspectLoader.get_source().

is_package(fullname)¶

Concrete implementation ofInspectLoader.is_package(). A moduleis determined to be a package if its file path (as provided byExecutionLoader.get_filename()) is a file named__init__ when the file extension is removedand the module nameitself does not end in__init__.

31.5.4.importlib.machinery – Importers and path hooks¶

Source code:Lib/importlib/machinery.py

This module contains the various objects that helpimportfind and load modules.

importlib.machinery.SOURCE_SUFFIXES¶

A list of strings representing the recognized file suffixes for sourcemodules.

New in version 3.3.

importlib.machinery.DEBUG_BYTECODE_SUFFIXES¶

A list of strings representing the file suffixes for non-optimized bytecodemodules.

New in version 3.3.

Deprecated since version 3.5:UseBYTECODE_SUFFIXES instead.

importlib.machinery.OPTIMIZED_BYTECODE_SUFFIXES¶

A list of strings representing the file suffixes for optimized bytecodemodules.

New in version 3.3.

Deprecated since version 3.5:UseBYTECODE_SUFFIXES instead.

importlib.machinery.BYTECODE_SUFFIXES¶

A list of strings representing the recognized file suffixes for bytecodemodules (including the leading dot).

New in version 3.3.

Changed in version 3.5:The value is no longer dependent on__debug__.

importlib.machinery.EXTENSION_SUFFIXES¶

A list of strings representing the recognized file suffixes forextension modules.

New in version 3.3.

importlib.machinery.all_suffixes()¶

Returns a combined list of strings representing all file suffixes formodules recognized by the standard import machinery. This is ahelper for code which simply needs to know if a filesystem pathpotentially refers to a module without needing any details on the kindof module (for example,inspect.getmodulename()).

New in version 3.3.

classimportlib.machinery.BuiltinImporter¶

Animporter for built-in modules. All known built-in modules arelisted insys.builtin_module_names. This class implements theimportlib.abc.MetaPathFinder andimportlib.abc.InspectLoader ABCs.

Only class methods are defined by this class to alleviate the need forinstantiation.

Changed in version 3.5:As part ofPEP 489, the builtin importer now implementsLoader.create_module() andLoader.exec_module()

classimportlib.machinery.FrozenImporter¶

Animporter for frozen modules. This class implements theimportlib.abc.MetaPathFinder andimportlib.abc.InspectLoader ABCs.

Only class methods are defined by this class to alleviate the need forinstantiation.

classimportlib.machinery.WindowsRegistryFinder¶

Finder for modules declared in the Windows registry. This classimplements theimportlib.abc.Finder ABC.

Only class methods are defined by this class to alleviate the need forinstantiation.

New in version 3.3.

classimportlib.machinery.PathFinder¶

AFinder forsys.path and package__path__ attributes.This class implements theimportlib.abc.MetaPathFinder ABC.

Only class methods are defined by this class to alleviate the need forinstantiation.

classmethodfind_spec(fullname,path=None,target=None)¶

Class method that attempts to find aspecfor the module specified byfullname onsys.path or, ifdefined, onpath. For each path entry that is searched,sys.path_importer_cache is checked. If a non-false objectis found then it is used as thepath entry finder to lookfor the module being searched for. If no entry is found insys.path_importer_cache, thensys.path_hooks issearched for a finder for the path entry and, if found, is storedinsys.path_importer_cache along with being queried aboutthe module. If no finder is ever found thenNone is bothstored in the cache and returned.

New in version 3.4.

Changed in version 3.5:If the current working directory – represented by an empty string –is no longer valid thenNone is returned but no value is cachedinsys.path_importer_cache.

classmethodfind_module(fullname,path=None)¶

A legacy wrapper aroundfind_spec().

Deprecated since version 3.4:Usefind_spec() instead.

classmethodinvalidate_caches()¶

Callsimportlib.abc.PathEntryFinder.invalidate_caches() on allfinders stored insys.path_importer_cache.

Changed in version 3.4:Calls objects insys.path_hooks with the current workingdirectory for'' (i.e. the empty string).

classimportlib.machinery.FileFinder(path,*loader_details)¶

A concrete implementation ofimportlib.abc.PathEntryFinder whichcaches results from the file system.

Thepath argument is the directory for which the finder is in charge ofsearching.

Theloader_details argument is a variable number of 2-item tuples eachcontaining a loader and a sequence of file suffixes the loader recognizes.The loaders are expected to be callables which accept two arguments ofthe module’s name and the path to the file found.

The finder will cache the directory contents as necessary, making stat callsfor each module search to verify the cache is not outdated. Because cachestaleness relies upon the granularity of the operating system’s stateinformation of the file system, there is a potential race condition ofsearching for a module, creating a new file, and then searching for themodule the new file represents. If the operations happen fast enough to fitwithin the granularity of stat calls, then the module search will fail. Toprevent this from happening, when you create a module dynamically, make sureto callimportlib.invalidate_caches().

New in version 3.3.

path¶

The path the finder will search in.

find_spec(fullname,target=None)¶

Attempt to find the spec to handlefullname withinpath.

New in version 3.4.

find_loader(fullname)¶

Attempt to find the loader to handlefullname withinpath.

invalidate_caches()¶

Clear out the internal cache.

classmethodpath_hook(*loader_details)¶

A class method which returns a closure for use onsys.path_hooks.An instance ofFileFinder is returned by the closure using thepath argument given to the closure directly andloader_detailsindirectly.

If the argument to the closure is not an existing directory,ImportError is raised.

classimportlib.machinery.SourceFileLoader(fullname,path)¶

A concrete implementation ofimportlib.abc.SourceLoader bysubclassingimportlib.abc.FileLoader and providing some concreteimplementations of other methods.

New in version 3.3.

name¶

The name of the module that this loader will handle.

path¶

The path to the source file.

is_package(fullname)¶

Return true ifpath appears to be for a package.

path_stats(path)¶

Concrete implementation ofimportlib.abc.SourceLoader.path_stats().

set_data(path,data)¶

Concrete implementation ofimportlib.abc.SourceLoader.set_data().

load_module(name=None)¶

Concrete implementation ofimportlib.abc.Loader.load_module() wherespecifying the name of the module to load is optional.

classimportlib.machinery.SourcelessFileLoader(fullname,path)¶

A concrete implementation ofimportlib.abc.FileLoader which canimport bytecode files (i.e. no source code files exist).

Please note that direct use of bytecode files (and thus not source codefiles) inhibits your modules from being usable by all Pythonimplementations or new versions of Python which change the bytecodeformat.

New in version 3.3.

name¶

The name of the module the loader will handle.

path¶

The path to the bytecode file.

is_package(fullname)¶

Determines if the module is a package based onpath.

get_code(fullname)¶

Returns the code object forname created frompath.

get_source(fullname)¶

ReturnsNone as bytecode files have no source when this loader isused.

load_module(name=None)¶

Concrete implementation ofimportlib.abc.Loader.load_module() wherespecifying the name of the module to load is optional.

classimportlib.machinery.ExtensionFileLoader(fullname,path)¶

A concrete implementation ofimportlib.abc.ExecutionLoader forextension modules.

Thefullname argument specifies the name of the module the loader is tosupport. Thepath argument is the path to the extension module’s file.

New in version 3.3.

name¶

Name of the module the loader supports.

path¶

Path to the extension module.

create_module(spec)¶

Creates the module object from the given specification in accordancewithPEP 489.

New in version 3.5.

exec_module(module)¶

Initializes the given module object in accordance withPEP 489.

New in version 3.5.

is_package(fullname)¶

ReturnsTrue if the file path points to a package’s__init__module based onEXTENSION_SUFFIXES.

get_code(fullname)¶

ReturnsNone as extension modules lack a code object.

get_source(fullname)¶

ReturnsNone as extension modules do not have source code.

get_filename(fullname)¶

Returnspath.

New in version 3.4.

classimportlib.machinery.ModuleSpec(name,loader,*,origin=None,loader_state=None,is_package=None)¶

A specification for a module’s import-system-related state.

New in version 3.4.

name¶

(__name__)

A string for the fully-qualified name of the module.

loader¶

(__loader__)

The loader to use for loading. For namespace packages this should beset toNone.

origin¶

(__file__)

Name of the place from which the module is loaded, e.g. “builtin” forbuilt-in modules and the filename for modules loaded from source.Normally “origin” should be set, but it may beNone (the default)which indicates it is unspecified.

submodule_search_locations¶

(__path__)

List of strings for where to find submodules, if a package (Noneotherwise).

loader_state¶

Container of extra module-specific data for use during loading (orNone).

cached¶

(__cached__)

String for where the compiled module should be stored (orNone).

parent¶

(__package__)

(Read-only) Fully-qualified name of the package to which the modulebelongs as a submodule (orNone).

has_location¶

Boolean indicating whether or not the module’s “origin”attribute refers to a loadable location.

31.5.5.importlib.util – Utility code for importers¶

Source code:Lib/importlib/util.py

This module contains the various objects that help in the construction ofanimporter.

importlib.util.MAGIC_NUMBER¶

The bytes which represent the bytecode version number. If you need help withloading/writing bytecode then considerimportlib.abc.SourceLoader.

New in version 3.4.

importlib.util.cache_from_source(path,debug_override=None,*,optimization=None)¶

Return thePEP 3147/PEP 488 path to the byte-compiled file associatedwith the sourcepath. For example, ifpath is/foo/bar/baz.py the returnvalue would be/foo/bar/__pycache__/baz.cpython-32.pyc for Python 3.2.Thecpython-32 string comes from the current magic tag (seeget_tag(); ifsys.implementation.cache_tag is not defined thenNotImplementedError will be raised).

Theoptimization parameter is used to specify the optimization level of thebytecode file. An empty string represents no optimization, so/foo/bar/baz.py with anoptimization of'' will result in abytecode path of/foo/bar/__pycache__/baz.cpython-32.pyc.None causesthe interpter’s optimization level to be used. Any other value’s stringrepresentation being used, so/foo/bar/baz.py with anoptimization of2 will lead to the bytecode path of/foo/bar/__pycache__/baz.cpython-32.opt-2.pyc. The string representationofoptimization can only be alphanumeric, elseValueError is raised.

Thedebug_override parameter is deprecated and can be used to overridethe system’s value for__debug__. ATrue value is the equivalent ofsettingoptimization to the empty string. AFalse value is the same assettingoptimization to1. If bothdebug_override anoptimizationare notNone thenTypeError is raised.

New in version 3.4.

Changed in version 3.5:Theoptimization parameter was added and thedebug_override parameterwas deprecated.

importlib.util.source_from_cache(path)¶

Given thepath to aPEP 3147 file name, return the associated source codefile path. For example, ifpath is/foo/bar/__pycache__/baz.cpython-32.pyc the returned path would be/foo/bar/baz.py.path need not exist, however if it does not conformtoPEP 3147 orPEP 488 format, aValueError is raised. Ifsys.implementation.cache_tag is not defined,NotImplementedError is raised.

New in version 3.4.

importlib.util.decode_source(source_bytes)¶

Decode the given bytes representing source code and return it as a stringwith universal newlines (as required byimportlib.abc.InspectLoader.get_source()).

New in version 3.4.

importlib.util.resolve_name(name,package)¶

Resolve a relative module name to an absolute one.

Ifname has no leading dots, thenname is simply returned. Thisallows for usage such asimportlib.util.resolve_name('sys',__package__) without doing acheck to see if thepackage argument is needed.

ValueError is raised ifname is a relative module name butpackage is a false value (e.g.None or the empty string).ValueError is also raised a relative name would escape its containingpackage (e.g. requesting..bacon from within thespam package).

New in version 3.3.

importlib.util.find_spec(name,package=None)¶

Find thespec for a module, optionally relative tothe specifiedpackage name. If the module is insys.modules,thensys.modules[name].__spec__ is returned (unless the spec would beNone or is not set, in which caseValueError is raised).Otherwise a search usingsys.meta_path is done.None isreturned if no spec is found.

Ifname is for a submodule (contains a dot), the parent module isautomatically imported.

name andpackage work the same as forimport_module().

New in version 3.4.

importlib.util.module_from_spec(spec)¶

Create a new module based onspec andspec.loader.create_module().

Ifspec.loader.create_module() does not returnNone, then anypre-existing attributes will not be reset. Also, noAttributeErrorwill be raised if triggered while accessingspec or setting an attributeon the module.

This function is preferred over usingtypes.ModuleType to create anew module asspec is used to set as many import-controlled attributes onthe module as possible.

New in version 3.5.

@importlib.util.module_for_loader¶

Adecorator forimportlib.abc.Loader.load_module()to handle selecting the propermodule object to load with. The decorated method is expected to have a callsignature taking two positional arguments(e.g.load_module(self,module)) for which the second argumentwill be the moduleobject to be used by the loader.Note that the decorator will not work on static methods because of theassumption of two arguments.

The decorated method will take in thename of the module to be loadedas expected for aloader. If the module is not found insys.modules then a new one is constructed. Regardless of where themodule came from,__loader__ set toself and__package__is set based on whatimportlib.abc.InspectLoader.is_package() returns(if available). These attributes are set unconditionally to supportreloading.

If an exception is raised by the decorated method and a module was added tosys.modules, then the module will be removed to prevent a partiallyinitialized module from being in left insys.modules. If the modulewas already insys.modules then it is left alone.

Changed in version 3.3:__loader__ and__package__ are automatically set(when possible).

Changed in version 3.4:Set__name__,__loader____package__unconditionally to support reloading.

Deprecated since version 3.4:The import machinery now directly performs all the functionalityprovided by this function.

@importlib.util.set_loader¶

Adecorator forimportlib.abc.Loader.load_module()to set the__loader__attribute on the returned module. If the attribute is already set thedecorator does nothing. It is assumed that the first positional argument tothe wrapped method (i.e.self) is what__loader__ should be setto.

Changed in version 3.4:Set__loader__ if set toNone, as if the attribute does notexist.

Deprecated since version 3.4:The import machinery takes care of this automatically.

@importlib.util.set_package¶

Adecorator forimportlib.abc.Loader.load_module() to set the__package__ attribute on the returned module. If__package__is set and has a value other thanNone it will not be changed.

Deprecated since version 3.4:The import machinery takes care of this automatically.

importlib.util.spec_from_loader(name,loader,*,origin=None,is_package=None)¶

A factory function for creating aModuleSpec instance basedon a loader. The parameters have the same meaning as they do forModuleSpec. The function uses availableloader APIs, such asInspectLoader.is_package(), to fill in any missinginformation on the spec.

New in version 3.4.

importlib.util.spec_from_file_location(name,location,*,loader=None,submodule_search_locations=None)¶

A factory function for creating aModuleSpec instance basedon the path to a file. Missing information will be filled in on thespec by making use of loader APIs and by the implication that themodule will be file-based.

New in version 3.4.

classimportlib.util.LazyLoader(loader)¶

A class which postpones the execution of the loader of a module until themodule has an attribute accessed.

This classonly works with loaders that defineexec_module() as control over what module typeis used for the module is required. For those same reasons, the loader’screate_module() method will be ignored (i.e., theloader’s method should only returnNone; this excludesBuiltinImporter andExtensionFileLoader). Finally,modules which substitute the object placed intosys.modules willnot work as there is no way to properly replace the module referencesthroughout the interpreter safely;ValueError is raised if such asubstitution is detected.

Note

For projects where startup time is critical, this class allows forpotentially minimizing the cost of loading a module if it is never used.For projects where startup time is not essential then use of this class isheavily discouraged due to error messages created during loading beingpostponed and thus occurring out of context.

New in version 3.5.

classmethodfactory(loader)¶

A static method which returns a callable that creates a lazy loader. Thisis meant to be used in situations where the loader is passed by classinstead of by instance.

suffixes=importlib.machinery.SOURCE_SUFFIXESloader=importlib.machinery.SourceFileLoaderlazy_loader=importlib.util.LazyLoader.factory(loader)finder=importlib.machinery.FileFinder(path,(lazy_loader,suffixes))