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pythoninstallationdistutils

Combine --user with --prefix error with setup.py install

I was trying to install Python packages a system I recently gained access to. I was trying to take advantage of Python's relatively new per user site-packages directory, and the new option --user. (The option is currently undocumented, however it exists for Python 2.6+; you can see the help by running python setup.py install --help.)

When I tried running

python setup.py install --user

on any package I downloaded, I always got the following error:

error: can't combine user with with prefix/exec_prefix/home or install_(plat)base

The error was extremely perplexing because, as you can see, I wasn't providing the --prefix, --exec-prefix, --install-base, or --install-platbase flags as command line options. I wasted a lot of time trying to figure out what the problem was. I document my answer below, in hopes to spare some other poor soul a few hours of yak shaving.

Solution

  • One time workaround:

    pip install --user --install-option="--prefix=" <package_name>

    or

    python setup.py install --user --prefix=

    Note that there is no text (not even whitespace) after the =.

    Do not forget the --user flag.

    Installing multiple packages:

    Create ~/.pydistutils.cfg (or equivalent for your OS/platform) with the following contents:

    [install]
prefix=

    Note that there is no text (not even whitespace) after the =.

    Then run the necessary pip install --user or python setup.py install --user commands. Do not forget the --user flag.

    Finally, remove or rename this file. Leaving this file present will cause issues when installing Python packages system-wide (i.e., without --user) as this user with this ~/.pydistutils.cfg.

    The cause of this issue

    This appears to be an issue with both OpenSUSE and RedHat, which has lead to a bug in virtualenv on these platforms.

    The error stems from a system-level distutils configuration file (in my case /usr/lib64/python2.6/distutils/distutils.cfg) where there was this

    [install]
prefix=/usr/local

    Basically, this is equivalent to always running the install command as install --prefix=/usr/local. You have to override this specification using one of the techniques above.