draw pictures using matplotlib

[xyysharon]

Thanks for the great py-pde work.
When I tried to draw pictures using matplotlib 3.5, there was a flash back. And then I switch to version 3.2, it works well.
My code is as below:

There is no error after execution, but the drawing window just flashes and exits.

[david-zwicker]

I could not reproduce the error. Could you please add additional information to the issue?!

It would be best if you could post the output of the script pde/scripts/show_environment.py, so I get your exact versions of installed packages. Moreover, a more detailed error description might also help – what do you mean by a "flash back"?