My Python Tkinter Experience- Building a small calculator with Tkinter

My Python Tkinter Experience- Building  a small calculator with Tkinter (*Still working on it)

from Tkinter import *
import tkMessageBox
import sys
class scanner:
    list1 = []
    def __init__(self,parent):
#        f = Frame(parent)
#        f.pack(padx=300,pady=100)
#        Label(root, text="__main__").pack(padx=0, pady=1)
        self.entrytext = StringVar()
        self.entrytext1 = StringVar()
        Label(root, text="first name", width=10).grid(row=0,column=0)
        Entry(root, textvariable=self.entrytext, width=10).grid(row=0,column=1)
        Label(root, text="last name", width=10).grid(row=1,column=0)
        Entry(root, textvariable=self.entrytext1, width=10).grid(row=1,column=1)
        Button(root, text="ADD", command=self.add).grid()
        Button(root, text="SUBTRACT", command=self.subtract).grid()
       
    def add(self):
        global a
        global b
        self.a=int(self.entrytext.get())
        self.b=int(self.entrytext1.get())
        print "result is", self.a+self.b
#        self.entrytext.delete(0,END)
#        tkMessageBox.showinfo(title='popup', message="hi "+self.entrytext.get())


    def subtract(self):
        global a
        global b
        self.a=int(self.entrytext.get())
        self.b=int(self.entrytext1.get())
        print "result is", self.a-self.b
   
   
root= Tk()
root.geometry("300x300")
calc = scanner(root)
root.mainloop()