“Here’s the issue as far as I understand it: On Windows operating systems, every process that has a window (i.e. any none-console application) also has a message loop, and each process can only have one message loop. The problem with PyQT and wxPython is that they will try to create their own message loops inside the Softimage process, which somehow leads to the whole process shutting down. I don’t know Linux that well, but the same issue should arise there.
It turns out that the solution to this is to run wxPython or PyQT on their own separate threads, so that both message loops will run in isolation from each other.
Apparently Houdini 9.5 had the same thing happening with PyQT, and its documentation contains a code sample that addresses this issue. All I had to do was repackage it inside a Softimage plug-in, although I used wxPython instead of PyQT because I’m more familiar with it. But it should be trivial to change the code to use PyQT instead.”