import tkinter as tk

window = tk.Tk()

frame_a = tk.Frame()

frame_b = tk.Frame()

label_a = tk.Label(text="I'm in frame a!", master=frame_a)
label_a.pack()

label_b = tk.Label(text="I'm in frame b!", master=frame_b)
label_b.pack()

#Reihenfolge der frames ist wichtig
frame_a.pack()
frame_b.pack()


window.mainloop()