代码：
# encoding:utf-8
import tkinter as tk
root = tk.Tk()
root.title("Small Calculator")
root.geometry('500x300')
var1 = tk.DoubleVar()
label1 = tk.Label(text="第一个数字", width=20, height=2)
label1.pack()
entry1 = tk.Entry(width=20)
entry1.pack()
var2 = tk.StringVar()
label2 = tk.Label(text="符号", width=20, height=2)
label2.pack()
entry2 = tk.Entry(width=20)
entry2.pack()
var3 = tk.DoubleVar()
label3 = tk.Label(text="第二个数字", width=20, height=2)
label3.pack()
entry3 = tk.Entry(width=20)
entry3.pack()
var4 = tk.DoubleVar()
label4 = tk.Label(text="结果", width=20, height=2)
label4.pack()
label5 = tk.Label(textvar=var4, width=30, height=1,)
label5.pack()
def clickFun():
global var1
global var2
global var3
global var4
va11 = int(entry1.get())
var2 = entry2.get()
var3 = int(entry3.get())
if var2 == '+':
var4.set(int(va11+var3))
elif var2 == '-':
var4.set(int(va11-var3))
elif var2 == '':
var4.set(int(va11*var3))
elif var2 == '/':
if var3 == 0:
var4.set("请重新输入数据")
else:
var4.set(int(va11/var3))
else:
var4.set("运算符出错，请重新输入数据")
button1 = tk.Button(text="完成" ,width=10, height=2, command=clickFun)
button1.pack()
root.mainloop()
