Since Python 3 you can use exec() instead of exec_() (in Python 2 exec was a keyword). > And the fact the label magically attaches to the app through some side

Since Python 3 you can use exec() instead of exec_() (in Python 2 exec was a keyword). > And the fact the label magically attaches to the app through some side effect is also confusing. Are you referring to the first "label.show()" example? Typically that pattern is rare (~once per app for the main window). Regarding attachment to the app; QApplication is a process-wide singleton. All objects belong to the same app.