Bulls and cows

Bulls and cows
You are encouraged to solve this task according to the task description, using any language you may know.

This is an old game played with pencil and paper that was later implemented on computer.

The task is for the program to create a four digit random number from the digits 1 to 9, without duplication. The program should ask for guesses to this number, reject guesses that are malformed, then print the score for the guess.

The score is computed as:

1. The player wins if the guess is the same as the randomly chosen number, and the program ends.
2. A score of one bull is accumulated for each digit in the guess that equals the corresponding digit in the randomly chosen initial number.
3. A score of one cow is accumulated for each digit in the guess that also appears in the randomly chosen number, but in the wrong position.

Python

<lang python>

Bulls and cows. A game pre-dating, and similar to, Mastermind.

import random

digits = '123456789' size = 4 chosen = .join(random.sample(digits,size))

1. print chosen # Debug

print I have chosen a number from %s unique digits from 1 to 9 arranged in a random order. You need to input a %i digit, unique digit number as a guess at what I have chosen % (size, size) guesses = 0 while True:

   guesses += 1
   while True:
       # get a good guess
       guess = raw_input('\nNext guess [%i]: ' % guesses).strip()
       if len(guess) == 4 and \
          all(char in digits for char in guess) \
          and len(set(guess)) == size:
           break
       print "Problem, try again. You need to enter %i unique digits from 1 to 9" % size
   if guess == chosen:
       print '\nCongratulations you guessed correctly in',guesses,'attempts'
       break
   bulls = cows = 0
   for i in range(size):
       if guess[i] == chosen[i]:
           bulls += 1
       elif guess[i] in chosen:
           cows += 1
   print '  %i Bulls\n  %i Cows' % (bulls, cows)</lang>

Sample output:

I have chosen a number from 4 unique digits from 1 to 9 arranged in a random order.
You need to input a 4 digit, unique digit number as a guess at what I have chosen

Next guess [1]: 79
Problem, try again. You need to enter 4 unique digits from 1 to 9

Next guess [1]: 7983
  2 Bulls
  2 Cows

Next guess [2]: 7938

Congratulations you guessed correctly in 2 attempts