Comment # 5 on bug 1136634 from Giacomo Comes

I have a user starting to learn matplotlib. He follows one of the many examples
available everywhere and on openSUSE it doesn't work.
It works on CentOS. On openSUSE if matplotlib is installed with pip, then the
example works. But if matplotlib is installed with zypper, the example does not
work. The reason is that the default backend defined in the openSUSE build is
Agg which does not produce any graphic output.

I suggest to change in the file matplotlib-setup.cfg in the source rpm the
line:
  backend = Agg
to
  backend = TkAgg
And, in such case, the rpm python3-matplotlib should require
python3-matplotlib-tk

As a workaround, I have suggested my user to add the line
  backend:tkagg
in ~/.config/matplotlib/matplotlibrc

Please make matplotlib work even for a beginner.
The default backend does not have to be tkagg pick anyone that shows some
graphic output.