from tkinter import *

master = Tk()

frame = Frame(master)

frame.pack(padx=10,pady=10)

v1 = StringVar()

v2 = StringVar()

v3 = StringVar()

def test(content):

    return content.isdigit()

testCMD=master.register(test)

e1=Entry(frame,width=10,textvariable=v1,validate="key",\

         validatecommand=(testCMD,'%P')).grid(row=0,column=0)

Label(frame,text="+").grid(row=0,column=1)

e2=Entry(frame,width=10,textvariable=v2,validate="key",\

         validatecommand=(testCMD,'%P')).grid(row=0,column=2)

Label(frame,text="=").grid(row=0,column=3)

e3=Entry(frame,width=10,textvariable=v3,state="readonly").grid(row=0,column=4)

def calc():

    result = int(v1.get()) + int(v2.get())

    v3.set(str(result))

Button(frame,text="计算结果",command=calc).grid(row=1,column=2,pady=5)

mainloop()