Python 2.6 Message box

#Unknown side engine by Steve Atchison, python 2.6 ,Sept 6 2010
from Tkinter import *
import tkMessageBox

def showresult():
    sqfeet=float(theAcres.get())*43560 #convert acres to square feet
    unknownSide= sqfeet/float(knownSide.get()) #calculate unknown side

    #Message box code
    tkMessageBox.showinfo('Unknown side','Unknown side is %.2f  ft'  % unknownSide)

    #clear dialog
    theAcres.delete(0,END)
    knownSide.delete(0,END)

#Tkinter code
root = Tk()

Label(root,text='Known side').pack()
knownSide=Entry(root)
knownSide.pack(padx=5,pady=5)

Label(root,text='Acres').pack()
theAcres=Entry(root)
theAcres.pack(padx=5,pady=5)

btn=Button(root,text='Find unknown side',command=showresult)
btn.pack()

root.mainloop()