site —- Site-specific configuration hook

Source code:Lib/site.py

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

Importing this module will append site-specific paths to the module search pathand add a few builtins, unless -S was used. In that case, 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 the site.main() function.

在 3.3 版更改: 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 uses sys.prefix and sys.exec_prefix; empty headsare skipped. For the tail part, it uses the empty string and thenlib/site-packages (on Windows) orlib/pythonX.Y/site-packages (on Unix and Macintosh). For eachof the distinct head-tail combinations, it sees if it refers to an existingdirectory, and if so, adds it to sys.path and also inspects the newlyadded path for configuration files.

在 3.5 版更改: Support for the "site-python" directory has been removed.

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

注解

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, adjust PATH 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.

For example, suppose sys.prefix and sys.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 and spam, and two pathconfiguration files, foo.pth and bar.pth. Assumefoo.pth contains the following:

  1. # foo package configuration
  2.  
  3. foo
  4. bar
  5. bletch

and bar.pth contains:

  1. # bar package configuration
  2.  
  3. bar

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

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

Note that bletch is omitted because it doesn't exist; the bardirectory precedes the foo directory because bar.pth comesalphabetically before foo.pth; and spam is omitted because it isnot mentioned in either path configuration file.

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 an ImportError or its subclassexception, and the exception's name attribute equals to 'sitecustomize',it is silently ignored. If Python is started without output streams available, aswith pythonw.exe on Windows (which is used by default to start IDLE),attempted output from sitecustomize is ignored. Any other exceptioncauses a silent and perhaps mysterious failure of the process.

After this, an attempt is made to import a module named usercustomize,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 of sys.path unlessdisabled by -s. If this import fails with an ImportError orits subclass exception, and the exception's name attribute equals to'usercustomize', it is silently ignored.

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

Readline configuration

On systems that support readline, this module will also import andconfigure the rlcompleter module, if Python is started ininteractive mode and without the -S option.The default behavior is enable tab-completion and to use~/.pythonhistory as the history save file. To disable it, delete (oroverride) the [sys.interactivehook]($6b9263b1c6aa1fbc.md#sys._interactivehook) attribute in yoursitecustomize or usercustomize module or yourPYTHONSTARTUP file.

在 3.4 版更改: Activation of rlcompleter and history was made automatic.

模块内容

  • 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 to sys.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 be None ifgetusersitepackages() hasn't been called yet. Default value is~/.local/lib/pythonX.Y/site-packages for UNIX and non-framework MacOS X builds, ~/Library/Python/X.Y/lib/python/site-packages for Macframework builds, and %APPDATA%\Python\PythonXY\site-packageson Windows. This directory is a site directory, which means that.pth files in it will be processed.

  • site.USER_BASE

  • Path to the base directory for the user site-packages. Can be None ifgetuserbase() hasn't been called yet. Default value is~/.local for UNIX and Mac OS X non-framework builds,~/Library/Python/X.Y for Mac framework builds, and%APPDATA%\Python for Windows. This value is used by Distutils tocompute the installation directories for scripts, data files, Python modules,etc. for the user installation scheme.See also PYTHONUSERBASE.

  • 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 版更改: 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 in sitecustomize or usercustomize (see above).

  • site.getsitepackages()

  • Return a list containing all global site-packages directories.

3.2 新版功能.

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

3.2 新版功能.

  • 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, respecting PYTHONNOUSERSITE and USER_BASE.

3.2 新版功能.

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

  1. $ python3 -m site --user-site
  2. /home/user/.local/lib/python3.3/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 of ENABLE_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 by os.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.

参见

PEP 370 — 分用户的 site-packages 目录