import tkinter as tk
base=tk.Tk()
fm1 = tk.Frame()
button1=tk.Button(base,text="push1")
button2=tk.Button(fm1,text="push2")
button3=tk.Button(fm1,text="push3")
button4=tk.Button(base,text="push4")

button1.pack(fill = 'both', expand = True)
fm1.pack(fill = 'both', expand = True)
button2.pack(side = tk.LEFT, fill = 'both', expand = True)
button3.pack(side = tk.LEFT, fill = 'both', expand = True)
button4.pack(fill = 'both', expand = True)
base.mainloop()