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 macOS). 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 “true” (case-insensitive), the system-level prefixes will not be searched for site-packages; otherwise they will.
A path configuration file is a file whose name has the form
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
import (followed by space or tab) are executed.
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 the
corresponding module(s) importable
(load 3rd-party import hooks, adjust
Any other initialization is supposed to be done upon a module’s
actual import, if and when it happens.
Limiting a code chunk to a single line is a deliberate measure
to discourage putting anything more complex here.
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
/usr/local/lib/pythonX.Y/site-packages with three
spam, and two path
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
directory precedes the
foo directory because
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 or its subclass
exception, and the exception’s
name attribute equals to
it is silently ignored. If Python is started without output streams available, as
pythonw.exe on Windows (which is used by default to start IDLE),
attempted output from
sitecustomize is ignored. Any other exception
causes a silent and perhaps mysterious failure of the process.
After this, an attempt is made to import a module named
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
-s. If this import fails with an
its subclass exception, and the exception’s
name attribute equals to
'usercustomize', it is silently ignored.
Note that for some non-Unix systems,
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
rlcompleter module, if Python is started in
interactive mode and without the
The default behavior is enable tab-completion and to use
~/.python_history as the history save file. To disable it, delete (or
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.
Truemeans that it is enabled and was added to
Falsemeans that it was disabled by user request (with
Nonemeans 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-packagesfor UNIX and non-framework macOS builds,
~/Library/Python/X.Y/lib/python/site-packagesfor macOS framework builds, and
%APPDATA%\Python\PythonXY\site-packageson Windows. This directory is a site directory, which means that
.pthfiles 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
~/.localfor UNIX and macOS non-framework builds,
~/Library/Python/X.Yfor macOS framework builds, and
%APPDATA%\Pythonfor 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.
- site.addsitedir(sitedir, known_paths=None)¶
Add a directory to sys.path and process its
.pthfiles. Typically used in
Return a list containing all global site-packages directories.
New in version 3.2.
New in version 3.2.
Return the path of the user-specific site-packages directory,
USER_SITE. If it is not initialized yet, this function will also set it, respecting
USER_BASE. To determine if the user-specific site-packages was added to
ENABLE_USER_SITEshould be used.
New in version 3.2.
Command Line Interface¶
site module also provides a way to get the user directories from the
$ 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:
the user site-packages directory is enabled,
1 if it was disabled by the
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
The initialization of the sys.path module search path – The initialization of