Using matplotlib inside a virtualenv on macOS

The GUI frameworks that matplotlib uses to display interactive figures don't play nicely with virtualenvs. Specifically, the default framework that is used on macOS breaks inside a virtualenv. To fix this, we need to tell matplotlib to use a different framework that works in a virtualenv. Thankfully, this is fairly straightforward. After installing matplotlib inside a virtualenv,

cd ~/.virtualenvs/<name>/lib/python3.5/site-packages/matplotlib/mpl-data

Open matplotlibrc and change

backend : macosx

to

backend : TkAgg