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python - 在循环中附加到列表会重置列表

问题描述

这是我的代码：

deckTypes = []
cardType = ["Spade", "Hearts", "Diamonds", "Clubs"]
cardValues = ["Ace", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, "J", "Q", "K"]
Values = [[1, 11], 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 10, 10]
for i in cardType:
    for j in cardValues:
        deckTypes.append(str(j) + " of " + str(i))
deck = dict(zip(deckTypes, Values*4))
z = 0
while z < 5:
    card = random.choice(list(deck))
    handValue = deck[card]
    hand = []
    hand.append(card)
    print(hand)
    z += 1

我正在尝试追加到列表hand，但每次循环结束时它都会重置列表。所以我明白了：

['1 of Spade']
['3 of Spade']
['2 of Clubs']
['K of Hearts']
['4 of Spade']

我怎样才能做到这一点？

['1 of Spade', '3 of Spade', '2 of Clubs', 'K of Hearts', '4 of Spade']

PS：这不是全部的代码，但我试图让它尽可能清晰易懂

标签： python

解决方案

您放错了hand.

使用您当前的代码，在每次迭代期间hand设置为：[] 

z = 0
while z < 5:
    hand = [] # Executed during each iteration
    hand.append(card)
    print(hand)
    z += 1

因此，在每次迭代之后，您都会得到一个只有 1 个元素的列表：

['1 of Spade']
['3 of Spade']
['2 of Clubs']
['K of Hearts']
['4 of Spade']

相反，您应该hand 在循环之前进行初始化，如下所示：

hand = [] # Executed once, before iterating
z = 0
while z < 5:
    hand.append(card)
    print(hand)
    z += 1

现在，您可以看到元素在每次迭代时都被正确地附加到您的列表中：

['1 of Spade']
['1 of Spade', '3 of Spade']
['1 of Spade', '3 of Spade', '2 of Clubs']
['1 of Spade', '3 of Spade', '2 of Clubs', 'K of Hearts']
['1 of Spade', '3 of Spade', '2 of Clubs', 'K of Hearts', '4 of Spade']

当您退出循环时，hand根据需要包含以下列表：

['1 of Spade', '3 of Spade', '2 of Clubs', 'K of Hearts', '4 of Spade']

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