from Tkinter import *
import math
root = Tk()
top = Frame(root)
top.pack(side='top')
hwframe = Frame(top)
hwframe.pack(side='top')
hwtext = Label(hwframe, text='Hello, World!')
hwtext.pack(side='top')
rframe = Frame(top)
rframe.pack(side='top')
r_label = Label(rframe, text='The sine of')
r_label.pack(side='left')
r = StringVar()
r.set('1.2')
r_entry = Entry(rframe, width=6, textvariable=r)
r_entry.pack(side='left')
s = StringVar()
def comp_s(event):
global s
s.set('%g' % math.sin(float(r.get()))) # construct string
r_entry.bind('', comp_s)
compute = Label(rframe, text=' equals ')
compute.pack(side='left')
s_label = Label(rframe, textvariable=s, width=12)
s_label.pack(side='left')
def quit(event=None):
root.destroy()
quit_button = Button(top, text='Goodbye, GUI World!', command=quit)
quit_button.pack(side='top')
root.bind('', quit)
root.mainloop()