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Path: blob/master/08-Milestone Project - 2/03-Milestone Project 2 - Complete Walkthrough Solution.ipynb
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Milestone Project 2 - Complete Walkthrough Solution
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!
Game Play
To play a hand of Blackjack the following steps must be followed:
Create a deck of 52 cards
Shuffle the deck
Ask the Player for their bet
Make sure that the Player's bet does not exceed their available chips
Deal two cards to the Dealer and two cards to the Player
Show only one of the Dealer's cards, the other remains hidden
Show both of the Player's cards
Ask the Player if they wish to Hit, and take another card
If the Player's hand doesn't Bust (go over 21), ask if they'd like to Hit again.
If a Player Stands, play the Dealer's hand. The dealer will always Hit until the Dealer's value meets or exceeds 17
Determine the winner and adjust the Player's chips accordingly
Ask the Player if they'd like to play again
Playing Cards
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.
The Game
Imports and Global Variables
** 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.**
Class Definitions
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"
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:
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.
TESTING: Just to see that everything works so far, let's see what our Deck looks like!
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.
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:
Let's see what these two cards are:
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.
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!
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:
Either technique is fine, it only depends on how you plan to start your game parameters.
Function Defintions
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.
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:
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.
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.
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.
QUICK NOTES ABOUT PRINT STATEMENTS:
The asterisk
*
symbol is used to print every item in a collection, and thesep='\n '
argument prints each item on a separate line.In the fourth line where we have
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
Step 10: Write functions to handle end of game scenarios
Remember to pass player's hand, dealer's hand and chips as needed.
And now on to the game!!
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.