This notebook walks through a proposed solution to the Blackjack Game milestone project. The approach to solving and the specific code used are only suggestions - there are many different ways to code this out, and yours is likely to be different!
To play a hand of Blackjack the following steps must be followed:
A standard deck of playing cards has four suits (Hearts, Diamonds, Spades and Clubs) and thirteen ranks (2 through 10, then the face cards Jack, Queen, King and Ace) for a total of 52 cards per deck. Jacks, Queens and Kings all have a rank of 10. Aces have a rank of either 11 or 1 as needed to reach 21 without busting. As a starting point in your program, you may want to assign variables to store a list of suits, ranks, and then use a dictionary to map ranks to values.
** Step 1: Import the random module. This will be used to shuffle the deck prior to dealing. Then, declare variables to store suits, ranks and values. You can develop your own system, or copy ours below. Finally, declare a Boolean value to be used to control while
loops. This is a common practice used to control the flow of the game.**
suits = ('Hearts', 'Diamonds', 'Spades', 'Clubs')
ranks = ('Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten', 'Jack', 'Queen', 'King', 'Ace')
values = {'Two':2, 'Three':3, 'Four':4, 'Five':5, 'Six':6, 'Seven':7, 'Eight':8, 'Nine':9, 'Ten':10, 'Jack':10,
'Queen':10, 'King':10, 'Ace':11}
import random
suits = ('Hearts', 'Diamonds', 'Spades', 'Clubs')
ranks = ('Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten', 'Jack', 'Queen', 'King', 'Ace')
values = {'Two':2, 'Three':3, 'Four':4, 'Five':5, 'Six':6, 'Seven':7, 'Eight':8, 'Nine':9, 'Ten':10, 'Jack':10,
'Queen':10, 'King':10, 'Ace':11}
playing = True
Consider making a Card class where each Card object has a suit and a rank, then a Deck class to hold all 52 Card objects, and can be shuffled, and finally a Hand class that holds those Cards that have been dealt to each player from the Deck.
Step 2: Create a Card Class
A Card object really only needs two attributes: suit and rank. You might add an attribute for "value" - we chose to handle value later when developing our Hand class.
In addition to the Card's __init__ method, consider adding a __str__ method that, when asked to print a Card, returns a string in the form "Two of Hearts"
class Card:
def __init__(self,suit,rank):
self.suit = suit
self.rank = rank
def __str__(self):
return self.rank + ' of ' + self.suit
Step 3: Create a Deck Class
Here we might store 52 card objects in a list that can later be shuffled. First, though, we need to instantiate all 52 unique card objects and add them to our list. So long as the Card class definition appears in our code, we can build Card objects inside our Deck __init__ method. Consider iterating over sequences of suits and ranks to build out each card. This might appear inside a Deck class __init__ method:
for suit in suits:
for rank in ranks:
In addition to an __init__ method we'll want to add methods to shuffle our deck, and to deal out cards during gameplay.
OPTIONAL: We may never need to print the contents of the deck during gameplay, but having the ability to see the cards inside it may help troubleshoot any problems that occur during development. With this in mind, consider adding a __str__ method to the class definition.
class Deck:
def __init__(self):
self.deck = [] # start with an empty list
for suit in suits:
for rank in ranks:
self.deck.append(Card(suit,rank)) # build Card objects and add them to the list
def __str__(self):
deck_comp = '' # start with an empty string
for card in self.deck:
deck_comp += '\n '+card.__str__() # add each Card object's print string
return 'The deck has:' + deck_comp
def shuffle(self):
random.shuffle(self.deck)
def deal(self):
single_card = self.deck.pop()
return single_card
TESTING: Just to see that everything works so far, let's see what our Deck looks like!
test_deck = Deck()
print(test_deck)
The deck has: Two of Hearts Three of Hearts Four of Hearts Five of Hearts Six of Hearts Seven of Hearts Eight of Hearts Nine of Hearts Ten of Hearts Jack of Hearts Queen of Hearts King of Hearts Ace of Hearts Two of Diamonds Three of Diamonds Four of Diamonds Five of Diamonds Six of Diamonds Seven of Diamonds Eight of Diamonds Nine of Diamonds Ten of Diamonds Jack of Diamonds Queen of Diamonds King of Diamonds Ace of Diamonds Two of Spades Three of Spades Four of Spades Five of Spades Six of Spades Seven of Spades Eight of Spades Nine of Spades Ten of Spades Jack of Spades Queen of Spades King of Spades Ace of Spades Two of Clubs Three of Clubs Four of Clubs Five of Clubs Six of Clubs Seven of Clubs Eight of Clubs Nine of Clubs Ten of Clubs Jack of Clubs Queen of Clubs King of Clubs Ace of Clubs
Great! Now let's move on to our Hand class.
Step 4: Create a Hand Class
In addition to holding Card objects dealt from the Deck, the Hand class may be used to calculate the value of those cards using the values dictionary defined above. It may also need to adjust for the value of Aces when appropriate.
class Hand:
def __init__(self):
self.cards = [] # start with an empty list as we did in the Deck class
self.value = 0 # start with zero value
self.aces = 0 # add an attribute to keep track of aces
def add_card(self,card):
self.cards.append(card)
self.value += values[card.rank]
def adjust_for_ace(self):
pass
TESTING: Before we tackle the issue of changing Aces, let's make sure we can add two cards to a player's hand and obtain their value:
test_deck = Deck()
test_deck.shuffle()
test_player = Hand()
test_player.add_card(test_deck.deal())
test_player.add_card(test_deck.deal())
test_player.value
14
Let's see what these two cards are:
for card in test_player.cards:
print(card)
Nine of Hearts Five of Hearts
Great! Now let's tackle the Aces issue. If a hand's value exceeds 21 but it contains an Ace, we can reduce the Ace's value from 11 to 1 and continue playing.
class Hand:
def __init__(self):
self.cards = [] # start with an empty list as we did in the Deck class
self.value = 0 # start with zero value
self.aces = 0 # add an attribute to keep track of aces
def add_card(self,card):
self.cards.append(card)
self.value += values[card.rank]
if card.rank == 'Ace':
self.aces += 1 # add to self.aces
def adjust_for_ace(self):
while self.value > 21 and self.aces:
self.value -= 10
self.aces -= 1
We added code to the add_card method to bump self.aces whenever an ace is brought into the hand, and added code to the adjust_for_aces method that decreases the number of aces any time we make an adjustment to stay under 21.
Step 5: Create a Chips Class
In addition to decks of cards and hands, we need to keep track of a Player's starting chips, bets, and ongoing winnings. This could be done using global variables, but in the spirit of object oriented programming, let's make a Chips class instead!
class Chips:
def __init__(self):
self.total = 100 # This can be set to a default value or supplied by a user input
self.bet = 0
def win_bet(self):
self.total += self.bet
def lose_bet(self):
self.total -= self.bet
A NOTE ABOUT OUR DEFAULT TOTAL VALUE:
Alternatively, we could have passed a default total value as an parameter in the __init__. This would have let us pass in an override value at the time the object was created rather than wait until later to change it. The code would have looked like this:
def __init__(self,total=100):
self.total = total
self.bet = 0
Either technique is fine, it only depends on how you plan to start your game parameters.
A lot of steps are going to be repetitive. That's where functions come in! The following steps are guidelines - add or remove functions as needed in your own program.
Step 6: Write a function for taking bets
Since we're asking the user for an integer value, this would be a good place to use try
/except
. Remember to check that a Player's bet can be covered by their available chips.
def take_bet(chips):
while True:
try:
chips.bet = int(input('How many chips would you like to bet? '))
except ValueError:
print('Sorry, a bet must be an integer!')
else:
if chips.bet > chips.total:
print("Sorry, your bet can't exceed",chips.total)
else:
break
We used a while
loop here to continually prompt the user for input until we received an integer value that was within the Player's betting limit.
A QUICK NOTE ABOUT FUNCTIONS:
If we knew in advance what we were going to call our Player's Chips object, we could have written the above function like this:
def take_bet():
while True:
try:
player_chips.bet = int(input('How many chips would you like to bet? '))
except ValueError:
print('Sorry, a bet must be an integer!')
else:
if player_chips.bet > player_chips.total:
print("Sorry, your bet can't exceed",player_chips.total)
else:
break
and then we could call the function without passing any arguments. This is generally not a good idea! It's better to have functions be self-contained, able to accept any incoming value than depend on some future naming convention. Also, this makes it easier to add players in future versions of our program!
Step 7: Write a function for taking hits
Either player can take hits until they bust. This function will be called during gameplay anytime a Player requests a hit, or a Dealer's hand is less than 17. It should take in Deck and Hand objects as arguments, and deal one card off the deck and add it to the Hand. You may want it to check for aces in the event that a player's hand exceeds 21.
def hit(deck,hand):
hand.add_card(deck.deal())
hand.adjust_for_ace()
Step 8: Write a function prompting the Player to Hit or Stand
This function should accept the deck and the player's hand as arguments, and assign playing as a global variable.
If the Player Hits, employ the hit() function above. If the Player Stands, set the playing variable to False - this will control the behavior of a while
loop later on in our code.
def hit_or_stand(deck,hand):
global playing # to control an upcoming while loop
while True:
x = input("Would you like to Hit or Stand? Enter 'h' or 's' ")
if x[0].lower() == 'h':
hit(deck,hand) # hit() function defined above
elif x[0].lower() == 's':
print("Player stands. Dealer is playing.")
playing = False
else:
print("Sorry, please try again.")
continue
break
Step 9: Write functions to display cards
When the game starts, and after each time Player takes a card, the dealer's first card is hidden and all of Player's cards are visible. At the end of the hand all cards are shown, and you may want to show each hand's total value. Write a function for each of these scenarios.
def show_some(player,dealer):
print("\nDealer's Hand:")
print(" <card hidden>")
print('',dealer.cards[1])
print("\nPlayer's Hand:", *player.cards, sep='\n ')
def show_all(player,dealer):
print("\nDealer's Hand:", *dealer.cards, sep='\n ')
print("Dealer's Hand =",dealer.value)
print("\nPlayer's Hand:", *player.cards, sep='\n ')
print("Player's Hand =",player.value)
QUICK NOTES ABOUT PRINT STATEMENTS:
The asterisk *
symbol is used to print every item in a collection, and the sep='\n '
argument prints each item on a separate line.
In the fourth line where we have
print('',dealer.cards[1])
the empty string and comma are there just to add a space.
Here we used commas to separate the objects being printed in each line. If you want to concatenate strings using the +
symbol, then you have to call each Card object's __str__ method explicitly, as with
print(' ' + dealer.cards[1].__str__())
Step 10: Write functions to handle end of game scenarios
Remember to pass player's hand, dealer's hand and chips as needed.
def player_busts(player,dealer,chips):
print("Player busts!")
chips.lose_bet()
def player_wins(player,dealer,chips):
print("Player wins!")
chips.win_bet()
def dealer_busts(player,dealer,chips):
print("Dealer busts!")
chips.win_bet()
def dealer_wins(player,dealer,chips):
print("Dealer wins!")
chips.lose_bet()
def push(player,dealer):
print("Dealer and Player tie! It's a push.")
while True:
# Print an opening statement
print('Welcome to BlackJack! Get as close to 21 as you can without going over!\n\
Dealer hits until she reaches 17. Aces count as 1 or 11.')
# Create & shuffle the deck, deal two cards to each player
deck = Deck()
deck.shuffle()
player_hand = Hand()
player_hand.add_card(deck.deal())
player_hand.add_card(deck.deal())
dealer_hand = Hand()
dealer_hand.add_card(deck.deal())
dealer_hand.add_card(deck.deal())
# Set up the Player's chips
player_chips = Chips() # remember the default value is 100
# Prompt the Player for their bet
take_bet(player_chips)
# Show cards (but keep one dealer card hidden)
show_some(player_hand,dealer_hand)
while playing: # recall this variable from our hit_or_stand function
# Prompt for Player to Hit or Stand
hit_or_stand(deck,player_hand)
# Show cards (but keep one dealer card hidden)
show_some(player_hand,dealer_hand)
# If player's hand exceeds 21, run player_busts() and break out of loop
if player_hand.value > 21:
player_busts(player_hand,dealer_hand,player_chips)
break
# If Player hasn't busted, play Dealer's hand until Dealer reaches 17
if player_hand.value <= 21:
while dealer_hand.value < 17:
hit(deck,dealer_hand)
# Show all cards
show_all(player_hand,dealer_hand)
# Run different winning scenarios
if dealer_hand.value > 21:
dealer_busts(player_hand,dealer_hand,player_chips)
elif dealer_hand.value > player_hand.value:
dealer_wins(player_hand,dealer_hand,player_chips)
elif dealer_hand.value < player_hand.value:
player_wins(player_hand,dealer_hand,player_chips)
else:
push(player_hand,dealer_hand)
# Inform Player of their chips total
print("\nPlayer's winnings stand at",player_chips.total)
# Ask to play again
new_game = input("Would you like to play another hand? Enter 'y' or 'n' ")
if new_game[0].lower()=='y':
playing=True
continue
else:
print("Thanks for playing!")
break
Welcome to BlackJack! Get as close to 21 as you can without going over! Dealer hits until she reaches 17. Aces count as 1 or 11. How many chips would you like to bet? 5 Dealer's Hand: <card hidden> Seven of Spades Player's Hand: Queen of Spades Nine of Hearts Dealer's Hand: Ace of Clubs Seven of Spades Dealer's Hand = 18 Player's Hand: Queen of Spades Nine of Hearts Player's Hand = 19 Player wins! Player's winnings stand at 105 Would you like to play another hand? Enter 'y' or 'n' y Welcome to BlackJack! Get as close to 21 as you can without going over! Dealer hits until she reaches 17. Aces count as 1 or 11. How many chips would you like to bet? 5 Dealer's Hand: <card hidden> Nine of Clubs Player's Hand: Queen of Diamonds Ace of Hearts Would you like to Hit or Stand? Enter 'h' or 's' s Player stands. Dealer is playing. Dealer's Hand: <card hidden> Nine of Clubs Player's Hand: Queen of Diamonds Ace of Hearts Dealer's Hand: Eight of Clubs Nine of Clubs Dealer's Hand = 17 Player's Hand: Queen of Diamonds Ace of Hearts Player's Hand = 21 Player wins! Player's winnings stand at 105 Would you like to play another hand? Enter 'y' or 'n' y Welcome to BlackJack! Get as close to 21 as you can without going over! Dealer hits until she reaches 17. Aces count as 1 or 11. How many chips would you like to bet? 65 Dealer's Hand: <card hidden> Four of Spades Player's Hand: Queen of Clubs Four of Diamonds Would you like to Hit or Stand? Enter 'h' or 's' h Dealer's Hand: <card hidden> Four of Spades Player's Hand: Queen of Clubs Four of Diamonds Eight of Diamonds Player busts! Player's winnings stand at 35 Would you like to play another hand? Enter 'y' or 'n' n Thanks for playing!
And that's it! Remember, these steps may differ significantly from your own solution. That's OK! Keep working on different sections of your program until you get the desired results. It takes a lot of time and patience! As always, feel free to post questions and comments to the QA Forums.