18.6: Add, remove, shuffle and sort

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To deal cards, we would like a method that removes a card from the deck and returns it. The list method pop provides a convenient way to do that:

#inside class Deck:

    def pop_card(self):
        return self.cards.pop()

Since pop removes the last card in the list, we are dealing from the bottom of the deck.

To add a card, we can use the list method append:

#inside class Deck:

    def add_card(self, card):
        self.cards.append(card)

A method like this that uses another method without doing much work is sometimes called a veneer. The metaphor comes from woodworking, where a veneer is a thin layer of good quality wood glued to the surface of a cheaper piece of wood to improve the appearance.

In this case add_card is a “thin” method that expresses a list operation in terms appropriate for decks. It improves the appearance, or interface, of the implementation.

As another example, we can write a Deck method named shuffle using the function shuffle from the random module:

# inside class Deck:
            
    def shuffle(self):
        random.shuffle(self.cards)

Don’t forget to import random.

As an exercise, write a Deck method named sort that uses the list method sort to sort the cards in a Deck. sort uses the __lt__ method we defined to determine the order.