Exercise 18. (Practice Python) Cows & Bulls

# Code written in PYTHON 3.6
# Cow & Bulls Game - a game where a 4 digit number will be generated automatically and user have to guess that number. 
# For every perfectly guessed digit at perfect place user get a cow
# For every perfectly guessed digit at wrong place user get a Bull {Bull = Total matching digit - cows}
# game continues untill player guess the number exactly {4 cows} At the end the code will show how many guess count.
# Any improvement suggestion are welcome. Am a learner ready to Learn new things.


import random

def cowBull_loop():
    ask= str(input("enter a four digit number: "))
    cow=0
    bullCow=0  #total number of digit guessed perfectly. right place + wrong place
    for i in range(0,4):
        if num[i]==ask[i]:
            cow+=1
    for i in num:
        if i in ask:
            bullCow +=1
    bull=bullCow-cow
    print("you have {} cow and {} bulls".format(cow,bull))
    return cow


if __name__=='__main__':
    num= str(random.randrange(1000,9999)) # for testing use str(2727)
    cow= 0
    count=0
    while cow !=4:
        count+=1
        cow = cowBull_loop()

The review still has a problem. When the num created has a repeted number (lets say 11ab) and someone guesses only one number correctly of the num (eg: 1cde), the game will return 1 cow and 1 bull or 2 bulls instead of only 1