new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  """Exercise 18: Cows And Bulls
  
  Create a program that will play the “cows and bulls” game with the user.
  The game works like this:
  
  Randomly generate a 4-digit number. Ask the user to guess a 4-digit
  number.
  For every digit that the user guessed correctly in the correct place,
  they have a “cow”. For every digit the user guessed correctly in the
  wrong place is a “bull.” Every time the user makes a guess, tell them
  how many “cows” and “bulls” they have. Once the user guesses the correct
  number, the game is over.
  Keep track of the number of guesses the user makes throughout teh game
  and tell the user at the end.
  
  Say the number generated by the computer is 1038. An example interaction
  could look like this:
  
      Welcome to the Cows and Bulls Game!
      Enter a number:
      >>> 1234
      2 cows, 0 bulls
      >>> 1256
      1 cow, 1 bull
  
  Until the user guesses the number.
  """
  
  import random
  
  
  def get_secret_number():
      return str(random.randint(1000, 9999))
  
  
  def get_matches(secret, user):
      cows = bulls = 0
  
      for i in range(4):
          if secret[i] == user[i]:
              cows += 1
          if secret[i] in user:
              bulls += 1
  
      return cows, bulls
  
  
  guessed = False
  guesses = 0
  secret = get_secret_number()
  
  while not guessed:
      user = input("Guess a 4-digit number: ")
      guesses += 1
  
      if user == secret:
          guessed = True
  
      print("%i cows, %i bulls" % (get_matches(secret, user)))
  
  print("Congrats! The number was %i. You has %i guesses." % (secret, guesses))
  
subject: Create cows_and_bulls.py