Tkinter pack method confusion

Question

I cant understand why the pack manager wont let you pack LEFT AND RIGHT below top packed widgets. My expected output of the following code would be

 A
 B
C D         


        

Answer 1

A work-around is to pack the C + D frames in a temp LabelFrame, then you can just pack it underneath B.

import tkinter as tk

root = tk.Tk()
w, h = root.winfo_screenwidth(), root.winfo_screenheight()
root.state('zoomed')
root.geometry("%dx%d+0+0" % (w-15, h-75))
A = tk.LabelFrame(root,text='A', bd=2)
B = tk.LabelFrame(root,text='B', bd=2)

temp = tk.LabelFrame(root)

C = tk.LabelFrame(temp,text='C', bd=2)
D = tk.LabelFrame(temp,text='D', bd=2)
E = tk.LabelFrame(root,text='E', bd=2)

A.pack(fill=tk.BOTH, expand=tk.TRUE)
B.pack(fill=tk.BOTH, expand=tk.TRUE)
C.pack(side=tk.LEFT,fill=tk.BOTH, expand=tk.TRUE)
D.pack(side=tk.RIGHT,fill=tk.BOTH, expand=tk.TRUE)
temp.pack(expand=tk.TRUE, fill=tk.BOTH)
E.pack(side=tk.BOTTOM, fill=tk.BOTH, expand=tk.TRUE)

root.mainloop()