How to export PYTHONPATH when I activate a virtual environment on pyenv-virtualenv?

Question

I am using pyenv and its plugin pyenv-virtualenv.

My questions is: How to modify PYTHONPATH environment variable when I activate some virtual environment on pyenv-virtualenv?

$ pyenv activate myenv
$ echo $PYTHONPATH  # I want this variable!

When I used simple virtualenv, I could modify PYTHONPATH via editing virtualenv_home/your_env/bin/activate

export OLD_PYTHONPATH=$PYTHONPATH
export PYTHONPATH="/path/to/you/want"

Which file should I edit for pyenv-virtualenv?

Answer 1

You simply set PYTHONPATH as per normal, whether that is in your shell startup script or elsewhere. When you switch to a pyenv-controlled virtualenv with pyenv virtualenv, it will automatically append all the necessary directories for this virtualenv to sys.path, but any directories you defined in the PYTHONPATH variable will precede them.

Added based on discussion in comments below:

You can create hook scripts for a given pyenv command <command> in $PYENV_HOME/pyenv.d/<command>/. You can even do this for pyenv’s “porcelain” commands which aren’t normally called directly by the user.

It should be possible to create a hook for activate (which is implicitly called by pyenv-virtualenv when switching to a virtualenv) which parses the name of the virtualenv and sets $PYTHONPATH based on that.

Note: I’ve written pyenv hooks before but haven’t explicitly tested this solution.