27.13. site — Site-specific configuration hook

Source code: Lib/site.py

This module is automatically imported during initialization. The automatic import can be suppressed using the interpreter’s -S option.

Importing this module will append site-specific paths to the module search path.

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 heads are skipped. For the tail part, it uses the empty string and then lib/site-packages (on Windows) or lib/python|version|/site-packages and then lib/site-python (on Unix and Macintosh). For each of the distinct head-tail combinations, it sees if it refers to an existing directory, and if so, adds it to sys.path and also inspects the newly added path for configuration files.

A path configuration file is a file whose name has the form package.pth and exists in one of the four directories mentioned above; its contents are additional items (one per line) to be added to sys.path. Non-existing items are never added to sys.path, but no check is made that the item refers to a directory (rather than a file). No item is added to sys.path more than once. Blank lines and lines beginning with # are skipped. Lines starting with import (followed by space or tab) are executed.

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 (where only the first three characters of sys.version are used to form the installation path name). Suppose this has a subdirectory /usr/local/lib/pythonX.Y/site-packages with three subsubdirectories, foo, bar and spam, and two path configuration files, foo.pth and bar.pth. Assume foo.pth contains the following:

# foo package configuration

foo
bar
bletch

and bar.pth contains:

# bar package configuration

bar

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

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

Note that bletch is omitted because it doesn’t exist; the bar directory precedes the foo directory because bar.pth comes alphabetically before foo.pth; and spam is omitted because it is not mentioned in either path configuration file.

After these path manipulations, an attempt is made to import a module named sitecustomize, which can perform arbitrary site-specific customizations. If this import fails with an ImportError exception, it is silently ignored.

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

site.PREFIXES

A list of prefixes for site package directories

site.ENABLE_USER_SITE

Flag showing the status of the user site directory. True means the user site directory is enabled and added to sys.path. When the flag is None the user site directory is disabled for security reasons.

site.USER_SITE

Path to the user site directory for the current Python version or None

site.USER_BASE

Path to the base directory for user site directories

PYTHONNOUSERSITE

PYTHONUSERBASE

site.addsitedir(sitedir, known_paths=None)

Adds a directory to sys.path and processes its pth files.

site.getsitepackages()

Returns a list containing all global site-packages directories (and possibly site-python).

New in version 3.2.

site.getuserbase()

Returns the “user base” directory path.

The “user base” directory can be used to store data. If the global variable USER_BASE is not initialized yet, this function will also set it.

New in version 3.2.

site.getusersitepackages()

Returns the user-specific site-packages directory path.

If the global variable USER_SITE is not initialized yet, this function will also set it.

New in version 3.2.