Tkinter design using a simple addition calculator

Tkinter design using a simple addition calculator:

(1) In the digital input box, only numbers, other characters can not be entered when the input other characters will not be displayed and automatically remove these non-numeric characters in the input box.

(2) Results box read-only, so that the results can not be human to interference.

code show as below:

from tkinter import *

root=Tk()

# 计算器

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

v1=StringVar()
v2=StringVar()
v3=StringVar()

def test(content):
    return content.isdigit()

testcmd=root.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()

Operating results as follows: