Task: Bulls and cows_Player
C#: using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BullsAndCows
{
    class Program
    {
        const int ANSWER_SIZE = 4;

        static IEnumerable<string> Permutations(int size)
        {
            if (size > 0)
            {
                foreach (string s in Permutations(size - 1))
                    foreach (char n in "123456789")
                        if (!s.Contains(n))
                            yield return s + n;
            }
            else
                yield return "";
        }

        static IEnumerable<T> Shuffle<T>(IEnumerable<T> source)
        {
            Random random = new Random();
            List<T> list = source.ToList();
            while (list.Count > 0)
            {
                int ix = random.Next(list.Count);
                yield return list[ix];
                list.RemoveAt(ix);
            }
        }

        static bool ReadBullsCows(out int bulls, out int cows)
        {
            string[] input = Console.ReadLine().Split(',').ToArray();
            bulls = cows = 0;
            if (input.Length < 2)
                return false;
            else
                return int.TryParse(input[0], out bulls)
                    && int.TryParse(input[1], out cows);
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Bulls and Cows");
            Console.WriteLine("==============");
            Console.WriteLine();
            List<string> answers = Shuffle(Permutations(ANSWER_SIZE)).ToList();
            while (answers.Count > 1)
            {
                string guess = answers[0];
                Console.Write("My guess is {0}. How many bulls, cows? ", guess);
                int bulls, cows;
                if (!ReadBullsCows(out bulls, out cows))
                    Console.WriteLine("Sorry, I didn't understand that. Please try again.");
                else
                    for (int ans = answers.Count - 1; ans >= 0; ans--)
                    {
                        int tb = 0, tc = 0;
                        for (int ix = 0; ix < ANSWER_SIZE; ix++)
                            if (answers[ans][ix] == guess[ix])
                                tb++;
                            else if (answers[ans].Contains(guess[ix]))
                                tc++;
                        if ((tb != bulls) || (tc != cows))
                            answers.RemoveAt(ans);
                    }
            }
            if (answers.Count == 1)
                Console.WriteLine("Hooray! The answer is {0}!", answers[0]);
            else
                Console.WriteLine("No possible answer fits the scores you gave.");
        }
    }
}

Python: from itertools import permutations
from random import shuffle

try:
    raw_input
except:
    raw_input = input
try:
    from itertools import izip
except:
    izip = zip
    
digits = '123456789'
size = 4

def parse_score(score):
    score = score.strip().split(',')
    return tuple(int(s.strip()) for s in score)

def scorecalc(guess, chosen):
    bulls = cows = 0
    for g,c in izip(guess, chosen):
        if g == c:
            bulls += 1
        elif g in chosen:
            cows += 1
    return bulls, cows

choices = list(permutations(digits, size))
shuffle(choices)
answers = []
scores  = []

print ("Playing Bulls & Cows with %i unique digits\n" % size)
       
while True:
    ans = choices[0]
    answers.append(ans)
    
    score = raw_input("Guess %2i is %*s. Answer (Bulls, cows)? "
                      % (len(answers), size, ''.join(ans)))
    score = parse_score(score)
    scores.append(score)
    
    found =  score == (size, 0)
    if found:
        print ("Ye-haw!")
        break
    choices = [c for c in choices if scorecalc(c, ans) == score]
    if not choices:
        print ("Bad scoring? nothing fits those scores you gave:")
        print ('  ' +
               '\n  '.join("%s -> %s" % (''.join(an),sc)
                           for an,sc in izip(answers, scores)))
        break