加入Python列表理解

Question

我是Python新手，无法将函数转换为列表理解。修真涉及value功能，其中包含类如下：

class Card(object): 

    # Lists containing valid candidates for a card's rank and suit. 
    suits = [None, "spade", "club", "heart", "diamond"] 
    ranks = [None, "ace", "two", "three", "four", "five", "six", 
      "seven", "eight", "nine", "ten", "jack", "queen", "king"] 

    # Dictionary containing the ranks and their associative values. 
    values = {None:0, "ace":1, "two":2, "three":3, "four":4, 
       "five":5,"six":6,"seven":7, "eight":8,"nine":9, 
       "ten":10, "jack":10, "queen":10, "king":10} 

    def __init__(self, rank=None, suit=None): 
     """Constructor.""" 
     if rank not in self.ranks: 
      raise ValueError("Invalid rank.") 
     if suit not in self.suits: 
      raise ValueError("Invalid suit.") 
     self.rank = rank 
     self.suit = suit 

    def __str__(self): 
     """A string representation of the Card.""" 
     return "{0}:{1}".format(self.rank, self.suit) 

不同的类创建卡对象的列表，并定义了以下功能：

def value(self): 
    """Returns an int value containing the summed values of the hand's cards.""" 
    result = 0 
    for card in self.cards: 
     result += Card.values[card.rank] 
    return result 

从我可以看，value函数是一个列表理解的候选人，但我不能得到它的工作。我相信以下内容是正确的，但是我继续得到语法错误，我不知道我做错了什么。请注意，我是新来的Python和list解析：

def value(self): 
    result = [x += y for x = Card.values[y.rank] for y in self.cards] 

Answer 1

您可以简单地使用sum功能和发电机表达这样

def value(self): 
    return sum(Card.values[card.rank] for card in self.cards) 

如果您想使用列表理解，那么你就可以简单地转换使用列表中理解语法发电机表达式，像这样

def value(self): 
    return sum([Card.values[card.rank] for card in self.cards])