PEP 370 – Per user site-packages directory
- Christian Heimes <christian at python.org>
- Standards Track
- 2.6, 3.0
This PEP proposes a new a per user site-packages directory to allow users the local installation of Python packages in their home directory.
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 , Working Env  or Virtual Env .
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.
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)
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)
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)
user script directory
A directory for binaries and scripts.  It’s shared across Python versions and the destination directory for scripts.
- Unix (including Mac)
On Windows the Application Data directory (aka
APPDATA) was chosen
because it is the most designated place for application data. Microsoft
recommends that software doesn’t write to
USERPROFILE  and
My Documents is not suited for application data, either.  The code
doesn’t query the Win32 API, instead it uses the environment variable
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 administrator for more information. 
~/.local was chosen in favor over
~/.python because the
directory is already used by several other programs in analogy to
/usr/local.  
Mac OS X Notes
On Mac OS X Python uses ~/.local directory as well.  Framework builds
of Python include
~/Library/Python/2.6/site-packages as an additional
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 accidentally overwriting a
stdlib module. Stdlib modules can still be overwritten with
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 . 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
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
PYTHONUSERBASE. The default location is used
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
directory to the search paths for header files and libraries. It also
adds the lib/ directory to rpath.
site module gets two arguments
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 a menu item which opens the user site directory in a new explorer windows.
A reference implementation is available in the bug tracker. 
This document has been placed in the public domain.
Last modified: 2019-07-03 18:20:45 GMT