@Pythonic-person Unreal Engine allows you to build it as a library and embed into another app, provided that you can drive it. It needs native window messages and I'm not versed enough in python to give you specifics, but it sounds doable. Make sure to read through the UE EULA though, to be sure that whatever you plan to do is legally allowed by Epic.
Just as a comment though. You chose a very slow language (python) to do very expensive task (3D), bind it to a C++ library (pyqt), which adds overhead, interoperate it with external app that has no direct python API, and then drive it with native OS messages in a language that is not directly supported by that platform. In short you chose to do it the hardest and slowest possible way before you even started. It's your decision of course, but I would seriously reconsider.
