I don't know much about this but it seems to be due to the application Resume feature added in OS X 10.7 and has to do with the persistence of application windows.  Python itself does not create any such windows; they are created by the GUI toolkits used in Python applications, like Tk (used by the standard library tkinter) or other third-party modules that interface to other toolkits (PyQT, PyObjC, etc). I took a quick look and didn't see any application bundle keys that could be added to the Python.app Info.plist to disable persistence globally in a Python framework build and, even if there were one, I'm not sure that is desirable.  Perhaps the best way is for each tool kit to do it.  Ronald, anyone else: have any suggestions?

https://developer.apple.com/library/content/documentation/DataManagement/Conceptual/DocBasedAppProgrammingGuideForOSX/StandardBehaviors/StandardBehaviors.html