Python Mastermind Game Troubles

I'm a beginner to Python programming and have come upon an issue with my current assignment. The assignment reads as follows... Your program should secretly generate a 4-digit num

Solution 1:

You can solve your problem very elegantly with the Python function map(). (Not quite as elegantly as I originally thought, but still pretty nicely.)

guess = "1879" # or [ '1', '8', '7', '9' ]
answer = "1234"

map() works like this: you give it a function as its first argument, and one or more sequences as arguments following that. It then takes takes that function and applies it first to both the first elements, then to both the second elements, and so on. For instance:

>>> def f(a,b):
>>>  return a + b
>>> map( f, [1,2,3,4], [ 10, 20, 30, 40 ] )

[ 11, 22, 33, 44 ]

Now, you have two sequence of characters, "guess" and "answer". You could write a function that returns X if they're equal and - otherwise like this:

>>> def mastermind_hint( a, b ):
>>>   return "X" if a == b else "-"

That's not quite enough, you also need to put in the 'O's. For this you need to use the entire "answer" sequence at once:

>>> def mastermind_hint( a, b ):
>>>   if a == b: return "X"
>>>   if a in answer: return "O"
>>>   return "-"

Using map, we can apply that to the sequences you have:

>>> map( mastermind_hint, guess, answer )
[ "X", "-", "-", "-" ]

Now, right now we're giving away more information than we're supposed to because the positions of our hints correspond to the positions of the guess characters. A simple way to hide this information is to sort the sequence. Python has a sorted() function which does this:

>>> sorted( map( mastermind_hint, guess, answer ) )
[ "-", "-", "-", "X" ]

All that remains is to join this into a single string:

>>> "".join( sorted( map( mastermind_hint, guess, answer ) ) )
"---X"

Solution 2:

Very interesting homework I must say. I wish I'd get homework like this one.

Normally I don't provide full answers to homework but I solved this one for fun and you have tried to solve this on your own so here you go:

import random

def main():
    print '>> New game started.\n>> Good luck!\n'
    answer = generateAnswer()
    while True:
        userGuess = getUserGuess()
        if userGuess == answer:
            print '>> Congratulations, you won!'
            return
        print '>> The answer you provided is incorrect.\n>> Perhaps this hint will help you: '
        giveFeedback(answer, userGuess)

def generateAnswer():
    digits = [str(x) for x in range(10)]
    answer = ''
    for i in range(4):
        digit = random.sample(digits, 1)[0]
        digits.remove(digit)
        answer += digit
    return answer

def getUserGuess():
    while True:
        guess = raw_input('>> Please enter a 4-digit number: ').strip()
        if len(guess) != 4:
            continue
        guessIsValid = True
        for x in guess:
            if guess.count(x) != 1 or ord(x) not in range(48, 58):
                guessIsValid = False
                break
        if guessIsValid:
            return guess

def giveFeedback(answer, guess):
    for i in range(4):
        if guess[i] == answer[i]:
            print 'X',
            continue
        if guess[i] in answer:
            print 'O',
            continue
        print '-',
    print '\n'

if __name__ == '__main__':
    try:
        main()
    except Exception, e:
        print '>> Fatal error: %s' % e

I hope you'll find your answer in this piece of code.

Solution 3:

Here is an example that uses some more advance python idioms to improve readability and succinctness. This also makes it easier to make a more general solution such as for n digit answers for m base.

import random
from itertools import permutations   # for "lucky guess" Easter egg

def main(base=10, size=4):
    print 'New game started.\nGood luck!\n'
    answer, turn = list(genAnswer(range(base), size)), 1
    while True:
        hint = ['X' if a == g 
           else '0' if g in answer
           else '-' for a, g in zip(answer, guess(base, size))]
        if set(hint) == set(['X']):
            if turn == 1:
                choices = len(list(permutations(range(base), size)))
                print 'You won, lucky guess out of %d possible choices' % choices
            else:
                print 'Congratulations, you won in %d turns!' % turn
            return
        print '  Hint %d: %s' % (turn, ''.join(hint))
        turn += 1

def genAnswer(digits, size):
    '''Python generator function'''
    for i in range(size):
        choice = random.choice(digits)
        yield str(choice)
        digits.remove(choice)

def guess(base, size):
    '''Uses duck typing for error detection'''
    while True:
        guess = raw_input('>> Guess: ').strip()
        try:
            if int(guess, base) < base**size and len(set(guess)) == size:
                return guess
        except ValueError:
            pass
        print 'Enter %d unique digits from 0 to %d' % (size, base -1)

>>> main(6, 4)
New game started.
Good luck!

>> Guess: 1234
  Hint 1: 0-X-
>> Guess: 12345
Enter 4 unique digits from 0 to 5
>> Guess: 01227
Enter 4 unique digits from 0 to 5
>> Guess: 0123
  Hint 2: XX-0
>> Guess: 0135
Congratulations, you won in 3 turns!