I have loads of conda environments in parallel, some of which have Qt4 installed and some have Qt5. I used to have backend : Qt4Agg in my ~/.config/matplotlib/matplotlibrc, but nowadays this will get me errors when I'm in one of the Qt5-environments.

Ideally I would like to be able to specify backend : QtAgg and it should use either Qt5 or Qt4, whatever is available ad hoc.

I had a look at the backend selection stuff, but couldn't find how to do it. I'd propose to come up with a PR if somebody could give me a short tip, where to implement such a switch..