Qt for Python (PySide/Shiboken)

Let's try again 😜 I'm newbie in QtWidget, I have more experience in QML, but I think your layout lacks of HorizontalLayout. Then, in your UI function you set the MinimumWidth property, so defining the frame you have to set that instead of geometry. Last but not least: I think your UIFunctions class have to subclass Window, to gain access to frm_left_menu. I think you can take inspiration from UI python file by original project (the ui_main.py )