How to tell Python to prefer module from $HOME/lib/python over /usr/lib/python?

Question

In Python, I'm getting an error because it's loading a module from /usr/lib/python2.6/site-packages but I'd like it to use my version in $HOME/python-modules/lib/python2.6/site-packages, which I installed using pip-python --install-option="--prefix=$HOME/python-modules --ignore-installed

How can I tell Python to use my version of the library? Setting PYTHONPATH to $HOME/python-modules/lib/python2.6/site-packages doesn't help, since /usr/lib/... apparently has precedence.

Answer 1

Take a look at the site module for ways to customize your environment.

One way to accomplish this is to add a file to a location currently on sys.path called usercustomize.py, when Python is starting up it will automatically import this file, and you can use it to modify sys.path.

First, set $PYTHONPATH to $HOME (or add $HOME if $PYTHONPATH has a value), then create the file $HOME/usercustomize.py with the following contents:

import sys, os
my_site = os.path.join(os.environ['HOME'],
                       'python-modules/lib/python2.6/site-packages')
sys.path.insert(0, my_site)

Now when you start Python you should see your custom site-packages directory before the system default on sys.path.

Answer 2

Newer Python versions now have built-in support to search the opendesktop location:

$HOME/.local/lib/pythonX.Y/site-packages

If you put your local modules there you don't have to any sys.path manipulations.