Project 3: Decks!

Goals!
The next project is an extension of the Card project from last week. Here you will get
a chance to define a new class that extends one of Python’s built-in types. Along the
way we will also explore random number generators, a topic described in the first part
of the textbook.!
Reading! !
Introduction to Computing Using Python, sections 6.4–6.5 and 8.1–8.5, plus
resources available on the class web site.!
Programming Projects!
1. Create a new file named Deck.py and add the definition of a class named Deck.
Your new class should be derived from Python’s list class. An instance of this
class will be a list of 52 Card objects (which are defined in Card.py). !
When the constructor is called it should return a list of all 52 cards in order from
2♣ up through A♠. !
Define three methods for your class:

• shuffle() should rearrange the cards into a new random permutation

• deal(n) should remove the first n cards from the deck and return them in a list

• restore(a) should add the cards in list a to the end of the deck!
d = Deck()!
len(d)!
52!
type(d[0])!
<class 'Card.Card'!
d!
[2♣, 3♣, 4♣, ... Q♠, K♠, A♠]!
d.shuffle()!
d!
[Q♣, A♦, 7♦, 9♦, 8♦, 3♠, 8♠, ... 5♣, 9♣, K♦]!
h = d.deal(5)!
h!
[Q♣, A♦, 7♦, 9♦, 8♦]!
d!
[3♠, 8♠, ... 5♣, 9♣, K♦]!
len(d)!
47!
CIS 211!
Spring 2014
Important: don’t define a
class that has a list as an
attribute. Define a class
that is a new type of list.
See the lecture notes on
the difference between

“has-a” and “is-a” d.restore(h)!
d!
[3♠, 8♠, ... 9♣, K♦, Q♣, A♦, 7♦, 9♦, 8♦]!
len(d)!
52!
d.sort()!
d!
[2♣, 3♣, 4♣, ... Q♠, K♠, A♠]!
Make sure you understand why the last expression above worked. Why are you
able to sort a deck of cards even though you did not define a sort method in
your class?!
2. Define a new class named PinochleDeck that has Deck as its base class. An
instance of this class should be a list of 48 cards. The game of Pinochle uses
only 9s and above, and there are two copies of each card. A new deck should be
sorted.!
d = PinochleDeck()!
d!
[9♣, 9♣, 10♣, 10♣, ... Q♠, Q♠, K♠, K♠, A♠, A♠]!
d.shuffle()!
h = d.deal(12)!
h.sort()!
h!
[A♣, 9♦, 10♦, J♦, J♦, 9♥, A♥, A♥, 9♠, 10♠, K♠, A♠]!
Card.pyc!
Near the front of your Deck.py file you need to have a statement that imports the
Card class:!
from Card import *!
You can either use the Card class you wrote for the last project, or you can download
a compiled binary of the class written by the instructors. This file, called Card.pyc
(note the ‘c’ on the end of the name), is available on Piazza and the CIS web page. If
you want to use this file download it and save it in the same directory as your
Deck.py file.!
Extra Credit Ideas!
• Since the Deck class is a subclass of Python’s list class users can do anything
to a Deck that they can do to a list, including some things they shouldn’t. For
example, it’s easy to attach a string to the end of a deck of cards:!
d!
[2♣, 3♣, 4♣, ... Q♠, K♠, A♠]!
d.append('howdy')!
len(d)!
53!
d.shuffle()!
d!
[5♣, 'howdy', 2♣, J♠, ... 8♥, J♣, Q♦]!
To make a random
permutation of a list you
can use a function
named shuffle from
Python’s random library
(see p. 197 in the
textbook).A function like points that expects a list of Card objects isn’t going to like that.!
Figure out what sorts of things you don’t want to happen with decks of cards and
add code to your class definition that raises an error message when the operation
is invoked. !
• Have the restore function verify its argument is a list of Card objects.!
• Write your own version of a method that makes a random permutation instead of
using random.shuffle. !
• Add a second (optional) argument to the deal method that specifies the number of
hands to create. For example, deal(5,2) will make 2 hands with 5 cards each,
where the cards are dealt in the traditional fashion, i.e. alternate cards to each
hand.!
Testing!
We will test your classes and functions by running the tests in a file named
test_Decks.py. You can download the file and run the tests yourself before you
submit your project. This is what you will see in your shell window when your code
passes all the tests:!
$ python3 -m unittest test_Decks.py !
....!
----------------------------------------------------------!
Ran 4 tests in 0.001s ! !
OK!
!