Command-line blackjack for up to 6 players in Python

Question

Here is command-line blackjack for up to 6 players (not including dealer). Would love any and all feedback!

"""
This is the code for a blackjack game.
"""

from random import shuffle
from time import sleep

def get_valid_response(query, valid_responses):
    response = raw_input(query)
    if response.lower() not in [r.lower() for r in valid_responses]:
        print "That is not a valid response. Try again."
        response = get_valid_response(query, valid_responses)

    return response

class Player:
    def __init__(self, name, game):
        self.cards = []
        self.name = name
        self.busted = False
        self.game = game

    def receive_card(self, card, is_face_up = True):
        card.is_face_up = is_face_up
        self.cards.append(card)

    def cards_string(self):
        return [card.to_string() for card in self.cards]


    def raw_points(self):
        return sum([card.points() for card in self.cards])

    def points(self):
        total = self.raw_points()
        # Check if we should reduce the value of aces
        if total > 21:
            ace_indices = [index for index, card in enumerate(self.cards) if card.rank == 'A']
            for ace_index in ace_indices:
                self.cards[ace_index].secondary_value = True
                if self.raw_points() <= 21:
                    return self.raw_points()

        return total

    def ask_for_decision(self):
        return get_valid_response("\nAttention {}!\nYou have {}. This totals {} points.\nWould you like to 'hit' or 'stay'? ".
                                  format(self.name, self.cards_string(), self.points()),
                                  ["hit", "stay"])

    def bust(self):
        print "\n{}, you have busted with {}. This totals {}!\n".format(self.name, self.cards_string(), self.points())
        self.busted = True

    def hit(self):
        self.game.deck.deal_card_to(self)
        if self.points() <= 21:
            self.play()
        else:
            self.bust()

    def stay(self):
        print "{} is staying with {}".format(self.name, self.points())

    def play(self):
        response = self.ask_for_decision()

        while response.lower() != 'hit' and response.lower() != 'stay':
            print "Not an acceptable response. You must 'hit' or 'stay'"
            response = self.ask_for_decision()

        if response.lower() == 'hit':
            self.hit()
        else:
            self.stay()


class Dealer(Player):
    def __init__(self, game):
        Player.__init__(self, "Dealer", game)

    def play(self):
        print "\nDealer is playing..."
        sleep(0.5)
        self.cards[0].is_face_up = True
        print "Dealer has {} for a total of {}".format(self.cards_string(), self.points())
        if self.points() <= 17:
            print "Dealer is hitting..."
            sleep(0.5)
            self.hit()
        else:
            print "Dealer is staying..."
            sleep(0.5)
            self.stay()

class Deck:
    def __init__(self):
        self.suits = ['Diamonds', 'Hearts', 'Clubs', 'Spades']
        self.ranks = ['A', '2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K']
        self.cards = [Card(suit, rank) for suit in self.suits for rank in self.ranks]

    def shuffle_cards(self):
        shuffle(self.cards)

    def deal_card_to(self, player, is_face_up = True):
        card = self.cards.pop()
        player.receive_card(card, is_face_up)

class Card:
    score_mapping = {
        'A': [11, 1],
        'K': [10],
        'Q': [10],
        'J': [10],
        '10': [10],
        '9': [9],
        '8': [8],
        '7': [7],
        '6': [6],
        '5': [5],
        '4': [4],
        '3': [3],
        '2': [2]
    }

    def __init__(self, suit, rank):
        self.suit = suit
        self.rank = rank
        self.is_face_up = None
        self.secondary_value = False

    def to_string(self):
        if not self.is_face_up:
            return "*"
        else:
            return "{}{}".format(self.rank, self.suit)

    def points(self):
        if self.secondary_value:
            return Card.score_mapping[self.rank][-1]
        else:
            return Card.score_mapping[self.rank][0]

class Game:
    def __init__(self, num_players):
        self.players = []
        for i in range(0, num_players):
            player = Player("Player {}".format(i + 1), self)
            self.players.append(player)

        self.dealer = Dealer(self)
        self.deck = Deck()
        self.deck.shuffle_cards()

    def print_state(self):
        for player in self.players + [self.dealer]:
            print "{} has cards: {}".format(player.name, player.cards_string())
            sleep(0.5)

        print

    def deal_initial_pair(self):
        # Deal one card face up to each player, deal one card face DOWN to himself
        print "Dealing first card to players..."
        self.deal_card_to_all(first_card=True)
        sleep(0.5)
        self.print_state()

        # Deal one card face up to each player, deal one card face UP to himself
        print "Dealing second card to players..."
        self.deal_card_to_all()
        sleep(0.5)

        self.print_state()

    def deal_card_to_all(self, first_card = False):
        for player in self.players:
            self.deck.deal_card_to(player, is_face_up = True)

        self.deck.deal_card_to(self.dealer, is_face_up = not first_card)

    def play_round(self):
        for player in [player for player in self.players if not player.busted]:
            player.play()

        self.dealer.play()

    def resolve(self):
        print "\n ---GAME RESULTS--- \n"
        sleep(0.5)

        if self.dealer.busted:
            print "Dealer has busted, so all non-busted players win!"
            print "Winners: {}".format(", ".join([player.name for player in self.players if not player.busted]))
            print "Busted players: {}".format(", ".join([player.name for player in self.players if player.busted]))

        else:
            for player in self.players:
                if player.busted:
                    print "Loser! {} has busted".format(player.name)
                elif player.points() < self.dealer.points():
                    print "Loser! {} has {} points. This is less than the dealer's total of {}.".format(player.name, player.points(), self.dealer.points())
                elif player.points() == self.dealer.points():
                    print "Tie! {} has {} points. This ties the dealer's total of {}.".format(player.name, player.points(), self.dealer.points())
                else:
                    print "Winner! {} has {} points. This is more than the dealer's total of {}. Congrats!".format(player.name, player.points(), self.dealer.points())


def play_game():
    num_players = get_num_players()
    print "Great! Let's play with {} players.".format(num_players)

    game = Game(num_players)
    game.deal_initial_pair()
    game.play_round()
    game.resolve()

    response = get_valid_response("Would you like to play again? ('yes' or 'no'): ", ['yes', 'no'])
    if response.lower() == "yes":
        play_game()
    else:
        print "Thanks for playing!"


def get_num_players():
    num_players_char = get_valid_response("How many players are playing today? (Please enter a number between 1 and 6): ",
                                         ['1', '2', '3', '4', '5', '6'])

    return int(num_players_char)


def main():
    play_game()

if __name__ == "__main__":
    main()

Answer 1

Code gives good overall impression.

Some micro-level suggestions:

• get rid of recursion in get_valid_response: all that will be safer with while-loop and break, usual pattern in Python
• remove [] in sum: generator will work just fine unless you are using very old Python.
• it's better to inherit from object. Your code uses classic classes at the moment.
• conversions to lower case at the border (near the input) will make your code cleaner.
• there are some PEP8 code style violations (eg, spaces around keyword argument) - check with a tool

Regarding object decomposition, classes, especially the Game class, mixes logic and presentation. But may be it's not a problem if the game is not intended to be part of a larger system, where other UI modalities will be used.

To decouple logic and presentation, well-known design approaches can be used, for example (but not necessarily!), MVC or similar. In short and oversimplifying, there will be VC-classes, dedicated to user interfaces (input/output), and M-classes, holding the model - mostly current classes, stripped of prints/inputs and representation concerns. You can also go four-tier (if it does not feel as overkill): presentation, business logic, data access, database. Specific choice depends on the larger system you think your software will be part of. It may well be that 2 layers are enough for your purposes for now (presentation + the rest).

For concrete example, instead of doing print, call i/o class methods, concerned with game communication. This way, specific way your code does it will not be tightly coupled with the rest of the game logic. You will be able to do, say, client-server for your game. Of course, which way communication is initiated, who pushes and who pulls data, will require some thinking. May well be in your architecture, that UI will call underlying game model objects.