How to change the default backend in matplotlib from ‘QtAgg’ to ‘Qt5Agg’ in Pycharm?

Qt5Agg is necessary to use the mayavi 3D visualization package. I have installed PyQt5 and mayavi using pip in a separate copied conda environment. The default backend then changes from TkAgg to QtAgg. This is a bit weird because in an earlier installation in a different PC the default changed directly to Qt5Agg. I always check the backend using the following commands from the python console :

import matplotlib 
matplotlib.get_backend()

Even with the backend being ‘QtAgg’, I am able to use mayavi from the terminal without any issue but not when I do so in Pycharm. Here I get a non-responsive empty window (image below) :

Image of the non-responsive window

I have been able to get rid of this issue by explicitly using Qt5Agg instead of QtAgg before the plt call :

import matplotlib
matplotlib.use('Qt5Agg')
import matplotlib.pyplot as plt

But I would prefer a better way than using the above in every script that I write. As I had mentioned earlier, I already have mayavi installed and have used it successfully it in Pycharm in a different PC and there the default backend is ‘Qt5Agg’ and hence there is no need to change the backend explicitly.

Is there anything obvious that I’m overlooking ? Can you please let me know of a way to change the default backend for matplotlib from QtAgg to Qt5Agg after PyQt5 installation using pip ?

Thanks in advance !!

Answer

Thanks to @PaulH’s comment, I was able to solve the issue. Owing to @mx0’s suggestion, I shall now explicitly mention the fix below so that others can also benefit from it.

In a particular conda environment, if matplotlib package is installed, then there will be a ‘matplotlibrc’ file stored somewhere that defines what the default backend will be whenever matplotlib is imported from that conda environment. The location of this ‘matplotlibrc’ can be found using the following commands :

import matplotlib
matplotlib.matplotlib_fname()

Please look into the following link if there’s any deprecation issue with the above commands :

https://matplotlib.org/stable/tutorials/introductory/customizing.html#customizing-with-matplotlibrc-files

Once the location of the ‘matplotlibrc’ file is known, open it and simply uncomment one line inside this file. Just change the backend from :

##backend: Agg

to :

backend: Qt5Agg

And that’s it. All the plot window troubles in PyCharm will be solved as far as the mayavi 3D visualization package is concerned. For any other use, where a specific backend is necessary, you can also set the default to any other backend of choice.