from Tkinter import *                 
from tkMessageBox import showinfo

def reply(name):
    showinfo(title='Reply', message='Hello %s!' % name)

top = Tk()
top.title('Echo')
top.iconbitmap('py-blue-trans-out.ico')

Label(top, text="Enter your name:").pack(side=TOP)
ent = Entry(top)
ent.pack(side=TOP)
btn = Button(top, text="Submit", command=(lambda: reply(ent.get())))
btn.pack(side=LEFT)

top.mainloop()