import random

number = random.randrange(1000,9999)

guess = []

guesses = 0

def start(number,guesses,guess):

    guess = raw_input("Please guess a 4-digit number : ")

    if int(guess) == number:
        print "You have guessed correctly after %d guesses. The number is %d" % (guesses, number)
    else:
        if int(guess) in range(1000,9999):
            guesses = guesses + 1
            check(number,guesses,guess)
        else:
            print "%r is not a 4-digit number" % guess
            start(number,guesses,guess)

def check(number,guesses,guess):

    #stringify inputs
    g = [i for i in str(guess)]
    n = [i for i in str(number)]

    #check against n

    iterate = [0,1,2,3]

    cows = []
    bulls = []

    for i in iterate:
        if g[i] == n[i]:
            cows.append(i)

        elif g[i] != n[i]:
            bulls.append(i)

    cows = len(cows)
    bulls = len(bulls)

    print "%d cows, %d bulls" % (cows,bulls)
    print "%d guesses" % guesses

    if guess != number:
        start(number,guesses,guess)


start(number,guesses,guess)