Source code: Lib/site.py
This module is automatically imported during initialization. The automatic import can be suppressed using the interpreter’s
Importing this module will append site-specific paths to the module search path and add a few builtins, unless
-S was used. In that case, this module can be safely imported with no automatic modifications to the module search path or additions to the builtins. To explicitly trigger the usual site-specific additions, call the
Changed in version 3.3: Importing the module used to trigger paths manipulation even when using
It starts by constructing up to four directories from a head and a tail part. For the head part, it uses
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/pythonX.Y/site-packages (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.
Changed in version 3.5: 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 and it is also checked for site-packages (sys.base_prefix and sys.base_exec_prefix will always be the “real” prefixes of the Python installation). If “pyvenv.cfg” (a bootstrap configuration file) contains the key “include-system-site-packages” set to anything other than “false” (case-insensitive), the system-level prefixes will still also be searched for site-packages; otherwise they won’t.
A path configuration file is a file whose name has the form
name.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, and 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.exec_prefix are set to
/usr/local. The Python X.Y library is then installed in
/usr/local/lib/pythonX.Y. Suppose this has a subdirectory
/usr/local/lib/pythonX.Y/site-packages with three subsubdirectories,
spam, and two path configuration files,
foo.pth contains the following:
# foo package configuration foo bar bletch
# bar package configuration bar
Then the following version-specific directories are added to
sys.path, in this order:
bletch is omitted because it doesn’t exist; the
bar directory precedes the
foo directory because
bar.pth comes alphabetically before
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. It is typically created by a system administrator in the site-packages directory. If this import fails with an
ImportError exception, it is silently ignored. If Python is started without output streams available, as with
pythonw.exe on Windows (which is used by default to start IDLE), attempted output from
sitecustomize is ignored. Any exception other than
ImportError causes 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, if
ENABLE_USER_SITE is true. This file is intended to be created in the user site-packages directory (see below), which is part of
sys.path unless disabled by
ImportError will be silently ignored.
Note that for some non-Unix systems,
sys.exec_prefix are empty, and the path manipulations are skipped; however the import of
usercustomize is still attempted.
On systems that support
readline, this module will also import and configure the
rlcompleter module, if Python is started in interactive 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 (or override) the
sys.__interactivehook__ attribute in your
usercustomize module or your
Changed in version 3.4: Activation of rlcompleter and history was made automatic.
A list of prefixes for site-packages directories.
Flag showing the status of the user site-packages directory.
True means that it is enabled and was added to
False means that it was disabled by user request (with
None means it was disabled for security reasons (mismatch between user or group id and effective id) or by an administrator.
Path to the user site-packages for the running Python. Can be
getusersitepackages() hasn’t been called yet. Default value is
~/.local/lib/pythonX.Y/site-packages for UNIX and non-framework Mac OS X builds,
~/Library/Python/X.Y/lib/python/site-packages for Mac framework builds, and
%APPDATA%\Python\PythonXY\site-packages on Windows. This directory is a site directory, which means that
.pth files in it will be processed.
Path to the base directory for the user site-packages. Can be
getuserbase() 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 to compute the installation directories for scripts, data files, Python modules, etc. for the user installation scheme. See also
Adds all the standard site-specific directories to the module search path. This function is called automatically when this module is imported, unless the Python interpreter was started with the
Changed in version 3.3: This function used to be called unconditionally.
Add a directory to sys.path and process its
.pth files. Typically used in
usercustomize (see above).
Return a list containing all global site-packages directories.
New in version 3.2.
New in version 3.2.
New in version 3.2.
site module also provides a way to get the user directories from the command line:
$ python3 -m site --user-site /home/user/.local/lib/python3.3/site-packages
If it is called without arguments, it will print the contents of
sys.path on the standard output, followed by the value of
USER_BASE and whether the directory exists, then the same thing for
USER_SITE, and finally the value of
Print the path to the user base directory.
Print the path to the user site-packages directory.
If both options are given, user base and user site will be printed (always in this order), separated by
If any option is given, the script will exit with one of these values:
O if the user site-packages directory is enabled,
1 if it was disabled by the user,
2 if it is disabled for security reasons or by an administrator, and a value greater than 2 if there is an error.
PEP 370 – Per user site-packages directory
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