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

Question

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.

Answer 1

Posting to save others time, as no available answers worked for me...

In some environments, using the --target (-t) switch will still hit the same error. In my testing on two flavors of linux, I encountered the same issue when using the --prefix= parameter.

Code:

PYTHONUSERBASE=/tmp/ pip install --user --force-reinstall $PACKAGE

Explanation: My workaround, which seems to work across many environments (MacOS, Amazon Linux, Debian) is to set the PYTHONUSERBASE environment variable to a temp location. --force-reinstall is used to trigger the local installation even when the package is already installed.

This will result in the module being compiled/installed (depending on the OS and Python version) to: /tmp/lib/python2.7/site-packages/*

Answer 2

As has been noted in the comments, the accepted answer (by @gotgenes, who, presumably, has genes) can lead to unexpected consequences.

@rogeleaderr says, "Note that keeping this file like this will make Python think that / is your root python library directory, leading to confusing issues if you try to install other new packages."

Rather than write a new config file, as @gotgenes recommends, a better option is to add --prefix= (with no text to the right of the equals sign) as an option on the command line, as in

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

Answer 3

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.