Python Tkinter菜单栏不显示

I'm trying to make a GUI using Tkinter and have come to implementing a menu bar. I've looked at a few tutorials and written some code for it, but a menu bar never seems to appear - just a blank frame with a white background. This doesn't just happen for my code though; on copying and pasting the code of one of the aforementioned tutorials into a new script, the same behaviour is exhibited.I'm trying to make a GUI using Tkinter and have