All examples are meant to be run as script.
In Spyder you can check

to not have your GUI interfere with the build-in IPython console.

I've struggled with this alot. I found that the workaround you suggested sometimes worked, sometimes didn't. I would really like something that worked in both Spyder and in a script.

Which part of the workaround, Issue 2?

I'm not too sure. I just remember not to ask too much of opening applications from within spyder. I'm mostly expressing my support for applications supporting execcution from within spyder. Though I know it is challenging with so many different versions out there in the wild.

I see, yeah I just tried out @ImportanceOfBeingErnest 's suggestion and using an external console is a good tool to be able to fall back on if needed. Though I like and am used to running everything within Spyder. While I have only been messing around with it recently for the past day or so, and using the most recent versions of spyder and matplotlib, I haven't had any issues with Kernel crashes or qapp.exec_() hanging using the workarounds I suggested. I noticed that there were quite a few forum threads out there that talked about this issue, so that is why I thought it might be nice to add a few extra lines or commented lines that would point people in the right direction. Though as you point out, what the 'right direction is' is complicated given the number of versions people might be using.

I'm going to close this based on @ImportanceOfBeingErnest comment. Our examples are not meant to be run inside spyder or any other IDE, particularly those that spawn an application - if you ned help getting Qt apps running in spyder, that's probably better discussed as a spyder or Qt issue. Thanks!

@gigo318 Could you open a PR with those changes?

I think it is good practice to always do the "is there a running Qt app?" dance before creating a QApplication so we should demo that.

Agreed with the change, however I think the QtWidgets.QApplication.setQuitOnLastWindowClosed(True) line should only be added when one is creating a new QApp, not when one is already present (on the basis of "if you're getting the QApp from someone else, assume that they have configured it the way they want").

Right now closing the window (in spyder) seems to return to the ipython console just fine, so I think this can be closed?

@anntzer It only works with "Execute in an external console".
"Execute in current console" still freezes at the second attempt. Is this expected/accepted?

Steps to reproduce:

• Copy code from https://matplotlib.org/gallery/user_interfaces/embedding_in_qt_sgskip.html in a file in Spyder.
• Run code, with "Execute in current console". -> ok
  (window appears, after closing the window, the console gets back to the prompt.
• Run code, with "Execute in current console" again.
  Observation: As opposed to the previeous run, the plot window now appears behind spyder.
  After closing the window, the console is still blocked.

I see the second plot appearing behind spyder, but not the blockage at the end that you report.
Looks like we can ensure the window to be raised to front even the second time by adding

app.activateWindow()
app.raise_()

before the call to qapp.exec_() -- see also https://github.com/matplotlib/matplotlib/pull/6384/files; this at least works for me locally.

After the second closing the commandline does not come back for me:

matplotlib 3.1.1
spyder 3.3.6
ipython 7.8.0
Qt 5.9.6
PyQt5 5.9.2

what about matplotlib master? what desktop environment?

Indeed, works on master 😄.

So after fixing the raise, this can be closed.

@anntzer Sorry, didn't see the label.