# print the lyrics of the song "Old McDonald had a farm"
# using functions to reduce your work
 
def print_exclamation():
    print 'Ee ai ee ai oh!'
 
def print_refrain():
    print 'Old McDonald had a farm.'
    print_exclamation()
 
def print_song(animal, sound):
    print_refrain()
    print 'And on his farm he had a ' + animal + '.'
    print_exclamation()
    print 'With a ' + 2 * (sound + ' ') + 'here,'
    print 'And a ' + 2 * (sound + ' ') + 'there.'
    print 'Here a ' + sound + ', there a ' + sound + '.'
    print 'Everywhere a ' + sound + ' ' + sound + '.'
    print_refrain()
 
print_song('cow', 'moo') # test it with the cow that sounds moo

# example of two labeled entries, button and result label
# uses grid to position widgets also sets focus/cursor
# a rather generic Tkinter GUI template for calculations
 
from Tkinter import *
 
def calculate():
    try:
        # get the enter1 and enter2 values
        num1 = float(enter1.get())
        num2 = float(enter2.get())
        # do the calculation
        result = num1 * num2
        # display the result string
        label3.config(text=str(result))
    except ValueError:
        label3.config(text='Enter numeric values!')
 
root = Tk()
#root.config(bg='yellow')
 
# first entry with label
label1 = Label(root, text='Enter a number:')
label1.grid(row=0, column=0)
enter1 = Entry(root, bg='yellow')
enter1.grid(row=1, column=0)
 
# second entry with label
label2 = Label(root, text='Enter another number:')
label2.grid(row=2, column=0)
enter2 = Entry(root, bg='yellow')
enter2.grid(row=3, column=0)
 
# do the calculation by clicking the button
btn1 = Button(root, text='Multiply Numbers', command=calculate)
btn1.grid(row=4, column=0)
 
# display the result in this label
label3 = Label(root)
label3.grid(row=5, column=0)
 
# start cursor in enter1
enter1.focus()
# value has been entered in enter1 now switch focus to enter2
enter1.bind('<Return>', func=lambda e:enter2.focus_set())
 
root.mainloop()

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