My contribution for http://www.practicepython.org/exercise/2014/07/05/18-cows-and-bulls.html

cowsandbulls.py

from random import randint, randrange

number = [randrange(1,9) for x in range(4)]
guesscount = 1

def game(guess):
	cows = 0
	bulls = 0
	global guesscount
	if guess != ''.join(str(x) for x in number):
		guesscount+=1
		for x in range(len(number)):
			if int(guess[x]) in number:
				if int(guess[x]) == number[x]:
					cows+=1
				else:
					bulls+=1
		print("{} cows, {} bull").format(cows,bulls)
	else:
		print("You got it! It took you %s guesses") % guesscount
		exit()

def main():
	while True:
		myguess = raw_input("Guess: ")
		game(myguess)

if __name__ == '__main__':
	main()