python - 如何正确实现/重载 "__repr__ "？

Question

刚接触 Python，这可能是一个愚蠢的问题，但是如何正确实现 repr 方法？

我编写了一个快速的小程序来模拟纸牌游戏，但我不知道为 repr 方法编写什么。 Card 类 的 repr 方法非常简单，但我不知道如何处理 DeckOfCards 类 这是我的代码:

import random
class Card:
'''Create a single card, by id number'''

# Class variables, created once for the class
    suits = [ '\u2660', '\u2661', '\u2662', '\u2663' ]
    ranks = [ 'A','2','3','4','5','6','7','8','9','10','J','Q','K' ]

    def __init__(self, n=0):
    # instance variables for _num, _rank, _suit, _value
    if 0 <= n < 52:
        self._num = n
        self._rank = Card.ranks[n%13]       # note referencing class vars
        self._suit = Card.suits[n//13]
        self._value = n%13 + 1
        if self._rank == 'A':
            self._value = 14
    else: # invalid card indicators
        self._rank = 'x'
        self._suit = 'x'
        self._value = -1

    def __repr__(self):
        return  self._rank + self._suit

    def __lt__(self,other):
        return self._value < other._value

    def __le__(self,other):
        return self._value <= other._value

    def __eq__(self,other):
        return self._value == other._value

class DeckOfCards:
'''A Deck is a collection of cards'''

    def __init__(self):
        self._deck = [ Card(i) for i in range(52) ]

    def __repr__(self):
        return 'Deck : ', self._deck

    def shuffle(self):
        return random.shuffle(self._deck)

    def deal_a_card(self, i=-1):
    #that way player can choose where to draw from 
        return self._deck.pop(i)

    def cards_left(self,count):
        return len(self._deck)

new_deck = DeckOfCards()

此外，请随意评论您想要的任何内容，无论是设计缺陷还是代码冗余，实际上是任何内容。提前致谢!

Answer 1

您应该返回字符串类型，例如在 Deck 中:

def __repr__(self):
    ...
    return 'Deck : '+str(self._deck)