#!/usr/bin/env python3

import tkinter as tk

root = tk.Tk()

frame0 = tk.Frame(root)
frame0.pack(side=tk.TOP, expand=tk.YES, fill=tk.BOTH)
frame1 = tk.Frame(root)
frame1.pack(side=tk.LEFT, expand=tk.YES, fill=tk.BOTH)
frame2 = tk.Frame(root)
frame2.pack(side=tk.LEFT, expand=tk.YES, fill=tk.BOTH)
frame3 = tk.Frame(root)
frame3.pack(side=tk.LEFT, expand=tk.YES, fill=tk.BOTH)
frame4 = tk.Frame(root)
frame4.pack(side=tk.LEFT, expand=tk.YES, fill=tk.BOTH)

entry1 = tk.Entry(frame0, width=25)

def button1_insert():
    entry1.insert(tk.END, 1)

entry1.pack(expand=tk.YES, fill=tk.X)

button1 = tk.Button(frame1, text='7', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button2 = tk.Button(frame1, text='4', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button3 = tk.Button(frame1, text='1', width=5, command=button1_insert).pack(expand=tk.YES, fill=tk.BOTH)
button4 = tk.Button(frame1, text='0', width=5).pack(expand=tk.YES, fill=tk.BOTH)

button5 = tk.Button(frame2, text='8', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button6 = tk.Button(frame2, text='5', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button7 = tk.Button(frame2, text='2', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button8 = tk.Button(frame2, text='.', width=5).pack(expand=tk.YES, fill=tk.BOTH)

button9 = tk.Button(frame3, text='9', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button10 = tk.Button(frame3, text='6', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button11 = tk.Button(frame3, text='3', width=5).pack(expand=tk.YES, fill=tk.BOTH)
button12 = tk.Button(frame3, text='=', width=5).pack(expand=tk.YES, fill=tk.BOTH)

button13 = tk.Button(frame4, text='<-', width=4).pack(expand=tk.YES, fill=tk.BOTH)
button14 = tk.Button(frame4, text='/', width=4).pack(expand=tk.YES, fill=tk.BOTH)
button15 = tk.Button(frame4, text='*', width=4).pack(expand=tk.YES, fill=tk.BOTH)
button16 = tk.Button(frame4, text='-', width=4).pack(expand=tk.YES, fill=tk.BOTH)
button17 = tk.Button(frame4, text='+', width=4).pack(expand=tk.YES, fill=tk.BOTH)

root.mainloop()