Inheritance

Here is a __str__ method for Deck:

#inside class Deck:

    def __str__(self):
        res = []
        for card in self.cards:
            res.append(str(card))
        return '\n'.join(res)

This method demonstrates an efficient way to accumulate a large string: building a list of strings and then using the string method join. The built-in function str invokes the __str__ method on each card and returns the string representation.

Since we invoke join on a newline character, the cards are separated by newlines. Here's what the result looks like:

>>> deck = Deck()
>>> print(deck)
Ace of Clubs
2 of Clubs
3 of Clubs
...
10 of Spades
Jack of Spades
Queen of Spades
King of Spades

Even though the result appears on 52 lines, it is one long string that contains newlines.