site --- Site-specific configuration hook

原始碼：Lib/site.py

This module is automatically imported during initialization. The automaticimport can be suppressed using the interpreter's-S option.

Importing this module normally appends site-specific paths to the module search pathand addscallables, includinghelp() to the built-innamespace. However, Python startup option-S blocks this and this modulecan be safely imported with no automatic modifications to the module search pathor additions to the builtins. To explicitly trigger the usual site-specificadditions, call themain() function.

在 3.3 版的變更:Importing the module used to trigger paths manipulation even when using-S.

It starts by constructing up to four directories from a head and a tail part.For the head part, it usessys.prefix andsys.exec_prefix; empty headsare skipped. For the tail part, it uses the empty string and thenlib/site-packages (on Windows) orlib/pythonX.Y[t]/site-packages (on Unix and macOS). (Theoptional suffix "t" indicates thefree threading build, and isappended if"t" is present in thesys.abiflags constant.)For eachof the distinct head-tail combinations, it sees if it refers to an existingdirectory, and if so, adds it tosys.path and also inspects the newlyadded path for configuration files.

在 3.5 版的變更:Support for the "site-python" directory has been removed.

在 3.13 版的變更:On Unix,Free threading Python installations areidentified by the "t" suffix in the version-specific directory name, such aslib/python3.13t/.

If a file named "pyvenv.cfg" exists one directory above sys.executable,sys.prefix and sys.exec_prefix are set to that directory andit is also checked for site-packages (sys.base_prefix andsys.base_exec_prefix will always be the "real" prefixes of the Pythoninstallation). If "pyvenv.cfg" (a bootstrap configuration file) containsthe key "include-system-site-packages" set to anything other than "true"(case-insensitive), the system-level prefixes will not besearched for site-packages; otherwise they will.

A path configuration file is a file whose name has the formname.pthand exists in one of the four directories mentioned above; its contents areadditional items (one per line) to be added tosys.path. Non-existing itemsare never added tosys.path, and no check is made that the item refers to adirectory rather than a file. No item is added tosys.path more thanonce. Blank lines and lines beginning with# are skipped. Lines startingwithimport (followed by space or tab) are executed.

備註

An executable line in a.pth file is run at every Python startup,regardless of whether a particular module is actually going to be used.Its impact should thus be kept to a minimum.The primary intended purpose of executable lines is to make thecorresponding module(s) importable(load 3rd-party import hooks, adjustPATH etc).Any other initialization is supposed to be done upon a module'sactual import, if and when it happens.Limiting a code chunk to a single line is a deliberate measureto discourage putting anything more complex here.

在 3.13 版的變更:The.pth files are now decoded by UTF-8 at first and then by thelocale encoding if it fails.

For example, supposesys.prefix andsys.exec_prefix are set to/usr/local. The Python X.Y library is then installed in/usr/local/lib/pythonX.Y. Suppose this hasa subdirectory/usr/local/lib/pythonX.Y/site-packages with threesubsubdirectories,foo,bar andspam, and two pathconfiguration files,foo.pth andbar.pth. Assumefoo.pth contains the following:

# foo package configurationfoobarbletch

andbar.pth contains:

# bar package configurationbar

Then the following version-specific directories are added tosys.path, in this order:

/usr/local/lib/pythonX.Y/site-packages/bar/usr/local/lib/pythonX.Y/site-packages/foo

Note thatbletch is omitted because it doesn't exist; thebardirectory precedes thefoo directory becausebar.pth comesalphabetically beforefoo.pth; andspam is omitted because it isnot mentioned in either path configuration file.

sitecustomize

After these path manipulations, an attempt is made to import a module namedsitecustomize, which can perform arbitrary site-specific customizations.It is typically created by a system administrator in the site-packagesdirectory. If this import fails with anImportError or its subclassexception, and the exception'snameattribute equals to'sitecustomize',it is silently ignored. If Python is started without output streams available, aswithpythonw.exe on Windows (which is used by default to start IDLE),attempted output fromsitecustomize is ignored. Any other exceptioncauses a silent and perhaps mysterious failure of the process.

usercustomize

After this, an attempt is made to import a module namedusercustomize,which can perform arbitrary user-specific customizations, ifENABLE_USER_SITE is true. This file is intended to be created in theuser site-packages directory (see below), which is part ofsys.path unlessdisabled by-s. If this import fails with anImportError orits subclass exception, and the exception'snameattribute equals to'usercustomize', it is silently ignored.

Note that for some non-Unix systems,sys.prefix andsys.exec_prefix areempty, and the path manipulations are skipped; however the import ofsitecustomize andusercustomize is still attempted.

Readline configuration

On systems that supportreadline, this module will also import andconfigure therlcompleter module, if Python is started ininteractive mode and without the-S option.The default behavior is enable tab-completion and to use~/.python_history as the history save file. To disable it, delete (oroverride) thesys.__interactivehook__ attribute in yoursitecustomize orusercustomize module or yourPYTHONSTARTUP file.

在 3.4 版的變更:Activation of rlcompleter and history was made automatic.

模組內容

site.PREFIXES

A list of prefixes for site-packages directories.

site.ENABLE_USER_SITE

Flag showing the status of the user site-packages directory.True meansthat it is enabled and was added tosys.path.False means that itwas disabled by user request (with-s orPYTHONNOUSERSITE).None means it was disabled for securityreasons (mismatch between user or group id and effective id) or by anadministrator.

site.USER_SITE

Path to the user site-packages for the running Python. Can beNone ifgetusersitepackages() hasn't been called yet. Default value is~/.local/lib/pythonX.Y[t]/site-packages for UNIX and non-frameworkmacOS builds,~/Library/Python/X.Y/lib/python/site-packages for macOSframework builds, and%APPDATA%\Python\PythonXY\site-packageson Windows. The optional "t" indicates the free-threaded build. Thisdirectory is a site directory, which means that.pth files in itwill be processed.

site.USER_BASE

Path to the base directory for the user site-packages. Can beNone ifgetuserbase() hasn't been called yet. Default value is~/.local for UNIX and macOS non-framework builds,~/Library/Python/X.Y for macOS framework builds, and%APPDATA%\Python for Windows. This value is used tocompute the installation directories for scripts, data files, Python modules,etc. for theuser installation scheme.See alsoPYTHONUSERBASE.

site.main()

Adds all the standard site-specific directories to the module searchpath. This function is called automatically when this module is imported,unless the Python interpreter was started with the-S flag.

在 3.3 版的變更:This function used to be called unconditionally.

site.addsitedir(sitedir,known_paths=None)

Add a directory to sys.path and process its.pth files. Typicallyused insitecustomize orusercustomize (see above).

site.getsitepackages()

Return a list containing all global site-packages directories.

在 3.2 版被加入.

site.getuserbase()

Return the path of the user base directory,USER_BASE. If it is notinitialized yet, this function will also set it, respectingPYTHONUSERBASE.

在 3.2 版被加入.

site.getusersitepackages()

Return the path of the user-specific site-packages directory,USER_SITE. If it is not initialized yet, this function will also setit, respectingUSER_BASE. To determine if the user-specificsite-packages was added tosys.pathENABLE_USER_SITE should beused.

在 3.2 版被加入.

命令列介面

Thesite module also provides a way to get the user directories from thecommand line:

$python-msite--user-site/home/user/.local/lib/python3.11/site-packages

If it is called without arguments, it will print the contents ofsys.path on the standard output, followed by the value ofUSER_BASE and whether the directory exists, then the same thing forUSER_SITE, and finally the value ofENABLE_USER_SITE.

--user-base

Print the path to the user base directory.

--user-site

Print the path to the user site-packages directory.

If both options are given, user base and user site will be printed (always inthis order), separated byos.pathsep.

If any option is given, the script will exit with one of these values:0 ifthe user site-packages directory is enabled,1 if it was disabled by theuser,2 if it is disabled for security reasons or by an administrator, and avalue greater than 2 if there is an error.

也參考