Working with multiple python packages in “editable” mode

Like a lot of pythonistas, I prefer doing my python development in virtual environments. Furthermore, I prefer virtualenvwrapper to manage my virtual environments. This ensures isolation of the environment and the packages that the project depends upon and this works extremely well for self contained projects.

Once in the while though, I need to create a dependency to a package that is being worked on in a different virtualenv. In other words, I need to simultaneously work in editable mode on 2 different packages from 2 different virtualenvs.

One of the ways to do this cleanly is to pip install the dependency into your virtualenv. However, each time you update the code for the dependency package, you also need to pip upgrade the package in your virtualenv. This becomes a pain if your dependency is a library that is shared across more than one virtualenv.

The other way to solve this is to also install the dependency in an editable mode, using pip install -e. However, with this approach again, you might end up having to constantly keep the source repo for the dependency package synced across all the virtualenvs that use it.

In both cases, you have multiple copies of the dependency lying around in your virtualenvs. How do you optimize this so that:

  1. There is just one copy of the dependency package.
  2. All virtualenvs get the latest changes in the dependency package without having to do anything special.
  3. Does not interfere or break the isolation of the virtualenv setup (ie: both, the dependency package and the dependent package are still in their own virtualenv)

A good clean way I recently discovered is using add2virtualenv

Perhaps a session capture is much better to explain this than loads of descriptive text:

[steve@lonelap ~]$ mkvirtualenv dependency
New python executable in dependency/bin/python2
Also creating executable in dependency/bin/python
Installing setuptools, pip...done.
[steve@lonelap (dependency)]$ echo 'print("Everyone needs me")' >
[steve@lonelap (dependency)]$ deactivate

[steve@lonelap ~]$ mkvirtualenv project
New python executable in project/bin/python2
Also creating executable in project/bin/python
Installing setuptools, pip...done.
[steve@lonelap (project)]$ echo "import dependency" >
[steve@lonelap (project)]$ echo "print('I am using dependency from %s' % dependency.__file__)" >>
[steve@lonelap (project)]$ python
Traceback (most recent call last):
  File "", line 1, in <module>
    import dependency
ImportError: No module named dependency
[steve@lonelap (project)]$ add2virtualenv ~/src/venvs/dependency
[steve@lonelap (project)]$ python
Everyone needs me
I am using dependency from /home/steve/src/venvs/dependency/dependency.pyc
[steve@lonelap (project)]$ deactivate

[steve@lonelap ~]$ workon dependency
[steve@lonelap (dependency)]$ echo "print('Dependency is now updated')" >>
[steve@lonelap (dependency)]$ deactivate

[steve@lonelap ~]$ workon project
[steve@lonelap (project)]$ python
Everyone needs me
Dependency is now updated
I am using dependency from /home/steve/src/venvs/dependency/
[steve@lonelap (project)]$