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18.5: Printing the deck

  • Page ID
    40840
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)

    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.


    18.5: Printing the deck is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey.

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