在 python 中使用 list.remove(value_of_the_list) 抛出 ValueError

Question

通过 list.remove(value) 函数从类型列表的全局变量中清除一些值时，出现错误 "ValueError: list.remove(x): x not in list"

我的 class 定义如下所示：

class Deck(object):
global_l_init = ['2h','2d','2s','2c','3h','3d','3s','3c','4h','4d','4s','4c',
'5h','5d','5s','5c','6h','6d','6s','6c','7h','7d','7s','7c',
'8h','8d','8s','8c','9h','9d','9s','9c','10h','10d','10s','10c',
'Jh','Jd','Js','Jc','Qh','Qd','Qs','Qc','Kh','Kd','Ks','Kc',
'Ah','Ad','As','Ac']
#Cards' value
d={'2h':2,'2d':2,'2s':2,'2c':2,'3h':3,'3d':3,'3s':3,'3c':3,
   '4h':4,'4d':4,'4s':4,'4c':4,'5h':5,'5d':5,'5s':5,'5c':5,
   '6h':6,'6d':6,'6s':6,'6c':6,'7h':7,'7d':7,'7s':7,'7c':7,
'8h':8,'8d':8,'8s':8,'8c':8,'9h':9,'9d':9,'9s':9,'9c':9,
'10h':10,'10d':10,'10s':10,'10c':10,'Jh':10,'Jd':10,'Js':10,
'Jc':10,'Qh':10,'Qd':10,'Qs':10,'Qc':10,'Kh':10,'Kd':10,'Ks':10,'Kc':10,
'Ah':10,'Ad':10,'As':10,'Ac':10,'Ah':1,'Ad':1,'As':1,'Ac':1}

def __init__(self,plr_cur_value):
    self.plr_cur_value = plr_cur_value

def deck_change(self):
    self.global_l_init.remove(self.plr_cur_value)

我检查它是如何工作的，是：

D1=Deck(['2h','Jh'])
D1.deck_change()

错误如下：

  ValueError                                Traceback (most recent call last)
<ipython-input-534-6f04c0ca0556> in <module>()
      1 D1=Deck(['2h','Jh'])
----> 2 D1.deck_change()

<ipython-input-528-7691239e1d5b> in deck_change(self)
     54 
     55     def deck_change(self):
---> 56         self.global_l_init.remove(self.plr_cur_value)
     57 

ValueError: list.remove(x): x not in list

我是 python 的新手。也许这个问题已经够愚蠢了。但仍然无法弄清楚为什么global_l_init定义为class变量不是accessed/changed？... 感谢您的回答。

Answer 1

根据您提供的代码，您在 remove 期望的（要从 list 中删除的单个项目）和您提供的（ list 个项目）。

您使用以下方法初始化您的实例：

D1=Deck(['2h','Jh'])

所以 self.plr_cur_value 是 ['2h','Jh']，这意味着您的 remove 调用等同于：

self.global_l_init.remove(['2h','Jh'])

remove 查看你的 global_l_init list（其中只有长度 2 str），试图查看它是否包含长度 2 list 的长度为 2 str（它不包含任何 list）。

如果目标是从 global_l_init 中删除每个元素，您需要更改：

self.global_l_init.remove(self.plr_cur_value)

至：

for card in self.plr_cur_value:
    self.global_l_init.remove(card)

让它单独移除每张卡片。

请注意，当您需要重复执行成员资格测试 (O(n))，或执行随机访问 list 插入或删除 (O(n) 每个）。由于您的所有值都是唯一的且不区分顺序，因此您最好在此处使用 set，它具有 O(1) 插入、删除和成员资格测试：

class Deck(object):
    #Cards' value
    d={'2h':2,'2d':2,'2s':2,'2c':2,'3h':3,'3d':3,'3s':3,'3c':3,
       '4h':4,'4d':4,'4s':4,'4c':4,'5h':5,'5d':5,'5s':5,'5c':5,
       '6h':6,'6d':6,'6s':6,'6c':6,'7h':7,'7d':7,'7s':7,'7c':7,
    '8h':8,'8d':8,'8s':8,'8c':8,'9h':9,'9d':9,'9s':9,'9c':9,
    '10h':10,'10d':10,'10s':10,'10c':10,'Jh':10,'Jd':10,'Js':10,
    'Jc':10,'Qh':10,'Qd':10,'Qs':10,'Qc':10,'Kh':10,'Kd':10,'Ks':10,'Kc':10,
    'Ah':10,'Ad':10,'As':10,'Ac':10,'Ah':1,'Ad':1,'As':1,'Ac':1}

    # Simplest way to make set here is to reuse d to make global_l_init w/o repeating yourself:
    global_l_init = set(d)

    def __init__(self,plr_cur_value):
        self.plr_cur_value = set(plr_cur_value)  # Convert to set on initialization

    def deck_change(self):
        # Optionally, make sure the cards are in the shared set before removing them
        # to match list.remove behavior of raising ValueError when card not found
        if not (self.plr_cur_value <= self.global_l_init):
            raise ValueError("Cards in hand are not in the deck: {}".format(
                    ', '.join(self.plr_cur_value - self.global_l_init)))

        # Bulk remove entire hand now that we know it's available
        self.global_l_init -= self.plr_cur_value

在 python 中使用 list.remove(value_of_the_list) 抛出 ValueError

In python while using list.remove(value_of_the_list) a ValueError is thrown

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