cows_and_buffaloes.py

from itertools import chain, combinations, permutations, product

class CB(object):
    def __init__(self):
        self.all = list(chain(*[permutations(i) for i in combinations(xrange(10), 4)]))
        self.seq = None
        self.cab = None
        self.cabs = [(i, j) for i, j in product(xrange(5), xrange(5)) if i + j <= 4]
        self.cabs.remove((3, 1))

    def _validate(self, seq):
        r = 0
        for s, s1 in zip(self.seq, seq):
            if s == s1:
                r += 1
        return list(self.cab) == [r, len(set(self.seq) & set(seq)) - r]

    def _result(self, seq, cab):
        self.seq = seq
        self.cab = cab
        return filter(self._validate, self.all)

    def update(self, seq, cab):
        self.all = self._result(seq, cab)
        self.analyze()

    def analyze(self, show=False):
        l = len(self.all)
        if l > 24 and show:
            if raw_input('-- are you sure? [y/n]: ') != 'y':
                show = False
        print '-'*12
        if l < 9 or show:
            print '\n'.join(map(str, self.all))
        else:
            print l
        print '-'*7
        out = ['_']*4
        for j in xrange(4):
            if all(i[j] == self.all[0][j] for i in self.all):
                out[j] = str(self.all[0][j])
        print ' '.join(out)
        print '-'*12

    def optimal(self, seq):
        all_, cab = max(
            ((self._result(seq, cab), cab) for cab in self.cabs),
            key=lambda x: len(x[0]))
        self.all = all_
        print '%sC %sB' % cab


def main():
    while True:
        cb1 = CB()
        cb2 = CB()
        while True:
            r = raw_input()
            if r == '0':
                cb2.analyze()
                break
            if r == '-1':
                return
            if r == 'show':
                cb1.analyze(show=True)
                continue
            l = [map(int, i) for i in r.split('-')]
            if len(l) == 2:
                cb1.update(*l)
            else:
                cb2.optimal(*l)

if __name__ == '__main__':
    main()