How do you set your pythonpath in an already-created virtualenv?

What file do I edit, and how? I created a virtual environment.

The most elegant solution to this problem is here.

Original answer remains, but this is a messy solution:

If you want to change the PYTHONPATH used in a virtualenv, you can add the following line to your virtualenv's bin/activate file:

export PYTHONPATH="/the/path/you/want"

This way, the new PYTHONPATH will be set each time you use this virtualenv.

EDIT: (to answer @RamRachum's comment)

To have it restored to its original value on deactivate, you could add

export OLD_PYTHONPATH="$PYTHONPATH"

before the previously mentioned line, and add the following line to your bin/postdeactivate script.

export PYTHONPATH="$OLD_PYTHONPATH"

The comment by @s29 should be an answer:

One way to add a directory to the virtual environment is to install virtualenvwrapper (which is useful for many things) and then do

mkvirtualenv myenv
workon myenv
add2virtualenv . #for current directory
add2virtualenv ~/my/path

If you want to remove these path edit the file myenvhomedir/lib/python2.7/site-packages/_virtualenv_path_extensions.pth

Documentation on virtualenvwrapper can be found at http://virtualenvwrapper.readthedocs.org/en/latest/

Specific documentation on this feature can be found at http://virtualenvwrapper.readthedocs.org/en/latest/command_ref.html?highlight=add2virtualenv

You can create a .pth file that contains the directory to search for, and place it in the {venv-root}/lib/{python-version}/site-packages directory. E.g.:

cd $(python -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())")
echo /some/library/path > some-library.pth

The effect is the same as adding /some/library/path to sys.path, and remain local to the virtualenv setup.