（Python 3.4 Tkinter）框架问题

Question

When I run this code:

from tkinter import *
root = Tk()

fr = Frame(root, width=50, height=50).pack()
b = Button(fr, text='Click').pack()

root.mainloop()

button 'b' is outside the frame 'fr', acting as if i wrote root instead of fr in b = Button(fr, ... .

Answer 1

You should execute pack on the object returned from Frame and Button.

fr = Frame(root, width=50, height=50)
fr.pack()
b = Button(fr, text='Click')
b.pack()

Otherwise, your fr and b are None, ie they take values returned by pack() which is None.