:mod:`site` --- Site-specific configuration hook
================================================
.. module:: site
:synopsis: Module responsible for site-specific configuration.
**Source code:** :source:`Lib/site.py`
--------------
.. highlightlang:: none
**This module is automatically imported during initialization.** The automatic
import can be suppressed using the interpreter's :option:`-S` option.
.. index:: triple: module; search; path
Importing this module will append site-specific paths to the module search path
and add a few builtins.
.. index::
pair: site-python; directory
pair: site-packages; directory
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
:file:`lib/site-packages` (on Windows) or
:file:`lib/python{X.Y}/site-packages` and then :file:`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 :file:`{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.
.. versionchanged:: 2.6
A space or tab is now required after the import keyword.
.. index::
single: package
triple: path; configuration; file
For example, suppose ``sys.prefix`` and ``sys.exec_prefix`` are set to
:file:`/usr/local`. The Python X.Y library is then installed in
:file:`/usr/local/lib/python{X.Y}`. Suppose this has
a subdirectory :file:`/usr/local/lib/python{X.Y}/site-packages` with three
subsubdirectories, :file:`foo`, :file:`bar` and :file:`spam`, and two path
configuration files, :file:`foo.pth` and :file:`bar.pth`. Assume
:file:`foo.pth` contains the following::
# foo package configuration
foo
bar
bletch
and :file:`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 :file:`bletch` is omitted because it doesn't exist; the :file:`bar`
directory precedes the :file:`foo` directory because :file:`bar.pth` comes
alphabetically before :file:`foo.pth`; and :file:`spam` is omitted because it is
not mentioned in either path configuration file.
.. index:: module: sitecustomize
After these path manipulations, an attempt is made to import a module named
:mod:`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 :exc:`ImportError` exception, it is
silently ignored. If Python is started without output streams available, as
with :file:`pythonw.exe` on Windows (which is used by default to start IDLE),
attempted output from :mod:`sitecustomize` is ignored. Any exception other
than :exc:`ImportError` causes a silent and perhaps mysterious failure of the
process.
.. index:: module: usercustomize
After this, an attempt is made to import a module named :mod:`usercustomize`,
which can perform arbitrary user-specific customizations, if
:data:`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 :option:`-s`. An :exc:`ImportError` will be 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
:mod:`sitecustomize` and :mod:`usercustomize` is still attempted.
.. data:: PREFIXES
A list of prefixes for site-packages directories.
.. versionadded:: 2.6
.. data:: ENABLE_USER_SITE
Flag showing the status of the user site-packages directory. ``True`` means
that it is enabled and was added to ``sys.path``. ``False`` means that it
was disabled by user request (with :option:`-s` or
:envvar:`PYTHONNOUSERSITE`). ``None`` means it was disabled for security
reasons (mismatch between user or group id and effective id) or by an
administrator.
.. versionadded:: 2.6
.. data:: USER_SITE
Path to the user site-packages for the running Python. Can be ``None`` if
:func:`getusersitepackages` hasn't been called yet. Default value is
:file:`~/.local/lib/python{X.Y}/site-packages` for UNIX and non-framework Mac
OS X builds, :file:`~/Library/Python/{X.Y}/lib/python/site-packages` for Mac
framework builds, and :file:`{%APPDATA%}\\Python\\Python{XY}\\site-packages`
on Windows. This directory is a site directory, which means that
:file:`.pth` files in it will be processed.
.. versionadded:: 2.6
.. data:: USER_BASE
Path to the base directory for the user site-packages. Can be ``None`` if
:func:`getuserbase` hasn't been called yet. Default value is
:file:`~/.local` for UNIX and Mac OS X non-framework builds,
:file:`~/Library/Python/{X.Y}` for Mac framework builds, and
:file:`{%APPDATA%}\\Python` for Windows. This value is used by Distutils to
compute the installation directories for scripts, data files, Python modules,
etc. for the :ref:`user installation scheme <inst-alt-install-user>`. See
also :envvar:`PYTHONUSERBASE`.
.. versionadded:: 2.6
.. function:: addsitedir(sitedir, known_paths=None)
Add a directory to sys.path and process its :file:`.pth` files. Typically
used in :mod:`sitecustomize` or :mod:`usercustomize` (see above).
.. function:: getsitepackages()
Return a list containing all global site-packages directories (and possibly
site-python).
.. versionadded:: 2.7
.. function:: getuserbase()
Return the path of the user base directory, :data:`USER_BASE`. If it is not
initialized yet, this function will also set it, respecting
:envvar:`PYTHONUSERBASE`.
.. versionadded:: 2.7
.. function:: getusersitepackages()
Return the path of the user-specific site-packages directory,
:data:`USER_SITE`. If it is not initialized yet, this function will also set
it, respecting :envvar:`PYTHONNOUSERSITE` and :data:`USER_BASE`.
.. versionadded:: 2.7
The :mod:`site` module also provides a way to get the user directories from the
command line:
.. code-block:: sh
$ python -m site --user-site
/home/user/.local/lib/python2.7/site-packages
.. program:: site
If it is called without arguments, it will print the contents of
:data:`sys.path` on the standard output, followed by the value of
:data:`USER_BASE` and whether the directory exists, then the same thing for
:data:`USER_SITE`, and finally the value of :data:`ENABLE_USER_SITE`.
.. cmdoption:: --user-base
Print the path to the user base directory.
.. cmdoption:: --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 in
this order), separated by :data:`os.pathsep`.
If any option is given, the script will exit with one of these values: ``0`` 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.
.. seealso::
:pep:`370` -- Per user site-packages directory