PEP: 370 Title: Per user site-packages directory Version: $Revision$ Last-Modified: $Date$ Author: Christian Heimes Status: Final Type: Standards Track Content-Type: text/x-rst Created: 11-Jan-2008 Python-Version: 2.6, 3.0 Post-History: Abstract ======== This PEP proposes a new a per user site-packages directory to allow users the local installation of Python packages in their home directory. Rationale ========= Current Python versions don't have a unified way to install packages into the home directory of a user (except for Mac Framework builds). Users are either forced to ask the system administrator to install or update a package for them or to use one of the many workarounds like Virtual Python [1]_, Working Env [2]_ or Virtual Env [3]_. It's not the goal of the PEP to replace the tools or to implement isolated installations of Python. It only implements the most common use case of an additional site-packages directory for each user. The feature can't be implemented using the environment variable *PYTHONPATH*. The env var just inserts a new directory to the beginning of *sys.path* but it doesn't parse the pth files in the directory. A full blown site-packages path is required for several applications and Python eggs. Specification ============= site directory (site-packages) A directory in ``sys.path``. In contrast to ordinary directories the pth files in the directory are processed, too. user site directory A site directory inside the users' home directory. A user site directory is specific to a Python version. The path contains the version number (major and minor only). Unix (including Mac OS X) ``~/.local/lib/python2.6/site-packages`` Windows ``%APPDATA%/Python/Python26/site-packages`` user data directory Usually the parent directory of the user site directory. It's meant for Python version specific data like config files, docs, images and translations. Unix (including Mac) ``~/.local/lib/python2.6`` Windows ``%APPDATA%/Python/Python26`` user base directory It's located inside the user's home directory. The user site and use config directory are inside the base directory. On some systems the directory may be shared with 3rd party apps. Unix (including Mac) ``~/.local`` Windows ``%APPDATA%/Python`` user script directory A directory for binaries and scripts. [10]_ It's shared across Python versions and the destination directory for scripts. Unix (including Mac) ``~/.local/bin`` Windows ``%APPDATA%/Python/Scripts`` Windows Notes ------------- On Windows the *Application Data* directory (aka ``APPDATA``) was chosen because it is the most designated place for application data. Microsoft recommands that software doesn't write to ``USERPROFILE`` [5]_ and ``My Documents`` is not suited for application data, either. [8]_ The code doesn't query the Win32 API, instead it uses the environment variable %APPDATA%. The application data directory is part of the roaming profile. In networks with domain logins the application data may be copied from and to the a central server. This can slow down log-in and log-off. Users can keep the data on the server by e.g. setting PYTHONUSERBASE to the value "%HOMEDRIVE%%HOMEPATH%\Applicata Data". Users should consult their local adminstrator for more information. [13]_ Unix Notes ---------- On Unix ``~/.local`` was chosen in favor over ``~/.python`` because the directory is already used by several other programs in analogy to ``/usr/local``. [7]_ [11]_ Mac OS X Notes -------------- On Mac OS X Python uses ~/.local directory as well. [12]_ Framework builds of Python include ``~/Library/Python/2.6/site-packages`` as an additional search path. Implementation ============== The site module gets a new method ``adduserpackage()`` which adds the appropriate directory to the search path. The directory is not added if it doesn't exist when Python is started. However the location of the user site directory and user base directory is stored in an internal variable for distutils. The user site directory is added before the system site directories but after Python's search paths and ``PYTHONPATH``. This setup allows the user to install a different version of a package than the system administrator but it prevents the user from accidently overwriting a stdlib module. Stdlib modules can still be overwritten with ``PYTHONPATH``. For security reasons the user site directory is *not* added to ``sys.path`` when the effective user id or group id is not equal to the process uid / gid [9]_. It's an additional barrier against code injection into suid apps. However Python suid scripts *must* always use the -E and -s option or users can sneak in their own code. The user site directory can be suppressed with a new option ``-s`` or the environment variable ``PYTHONNOUSERSITE``. The feature can be disabled globally by setting ``site.ENABLE_USER_SITE`` to the value ``False``. It must be set by editing ``site.py``. It can't be altered ``in sitecustomize.py`` or later. The path to the user base directory can be overwritten with the environment variable ``PYTHONUSERBASE``. The default location is used when ``PYTHONUSERBASE`` is not set or empty. ``distutils.command.install`` (setup.py install) gets a new argument ``--user`` to install packages in the user site directory. The required directories are created on demand. ``distutils.command.build_ext`` (setup.py build_ext) gets a new argument ``--user`` which adds the include/ and lib/ directories in the user base dirctory to the search paths for header files and libraries. It also adds the lib/ directory to rpath. The ``site`` module gets two arguments ``--user-base`` and ``--user-site`` to print the path to the user base or user site directory to the standard output. The feature is intended for scripting, e.g. ``./configure --prefix $(python2.5 -m site --user-base)`` ``distutils.sysconfig`` will get methods to access the private variables of site. (not yet implemented) The Windows updater needs to be updated, too. It should create an menu item which opens the user site directory in a new explorer windows. Backwards Compatibility ======================= TBD Reference Implementation ======================== A reference implementation is available in the bug tracker. [4]_ Copyright ========= This document has been placed in the public domain. References ========== .. [1] Virtual Python http://peak.telecommunity.com/DevCenter/EasyInstall#creating-a-virtual-python .. [2] Working Env http://pypi.python.org/pypi/workingenv.py http://blog.ianbicking.org/workingenv-revisited.html .. [3] Virtual Env http://pypi.python.org/pypi/virtualenv .. [4] reference implementation http://bugs.python.org/issue1799 http://svn.python.org/view/sandbox/trunk/pep370 .. [5] MSDN: CSIDL http://msdn2.microsoft.com/en-us/library/bb762494.aspx .. [6] Initial suggestion for a per user site-packages directory http://permalink.gmane.org/gmane.comp.python.devel/90902 .. [7] Suggestion of ~/.local/ http://permalink.gmane.org/gmane.comp.python.devel/90925 .. [8] APPDATA discussion http://permalink.gmane.org/gmane.comp.python.devel/90932 .. [9] Security concerns and -s option http://permalink.gmane.org/gmane.comp.python.devel/91063 .. [10] Discussion about the bin directory http://permalink.gmane.org/gmane.comp.python.devel/91095 .. [11] freedesktop.org XGD basedir specs mentions ~/.local http://www.freedesktop.org/wiki/Specifications/basedir-spec .. [12] ~/.local for Mac and usercustomize file http://permalink.gmane.org/gmane.comp.python.devel/91167 .. [13] Roaming profile on Windows http://permalink.gmane.org/gmane.comp.python.devel/91187 .. 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