Python：从for循环返回列表

Question

所以我有

packs_purchased = (10, 6, 36)
dice_purchased = (2, 0, 1)
board_games_purchased = (3, 2, 0)

和

prices = (4.25, 125, 11, 50)

我如何让这个 for 循环返回一个列表而不仅仅是输出

for packs_purchased in packs_purchased:
    if packs_purchased < 35:
        packs_spent = packs_purchased * prices[0]
    else:
        packs_spent = (int(math.floor(packs_purchased / 36)) * prices[1]) + ((packs_purchased % 36) * prices[0])
    print("%.2f" % packs_spent)

现在打印出来

42.50
25.50
125.00

我希望它返回一个列表，类似于

packs_spent(42.50, 25.50, 125.00)

Answer 1

只需在 for 循环之前创建一个列表，然后附加到该列表而不是打印。

packs_spent = []
for pack in packs_purchased:
    if pack < 35:
        spent = pack * prices[0]
    else:
        spent = (int(math.floor(pack / 36)) * prices[1]) + ((pack % 36) * prices[0])
    packs_spent.append(spent)

print(packs_spent)
# [42.5, 25.5, 125.0]

要以正确的小数位数和问题中显示的格式打印，您可以使用列表推导：

print("packs_spent(", 
      ', '.join(f"{i:.2f}" for i in packs_spent),
      ")",
      sep="")
# packs_spent(42.50, 25.50, 125.00)

Answer 2

只需声明一个空列表并将结果附加到该列表中。

packs_list = []    
for packs_purchased in packs_purchased:
   if packs_purchased < 35:
        packs_spent = packs_purchased * prices[0]
   else:
        packs_spent = (int(math.floor(packs_purchased / 36)) * prices[1]) + ((packs_purchased % 36) * prices[0])
packs_list.append(packs_spent)
print(packs_list)

Answer 3

您的 Python 代码中有一些愚蠢的错误以及一些样式错误（但我们不会去那里，因为它并不那么重要）。

错误包括，您将相同的variable 用于迭代变量以及iterable，在将来使用iterable 时可能会造成很大的混乱，并且您可能会得到int 而不是@ 987654327@.

另外，旁注，list comprehension 在local 范围内有变量，而不是global，因此不会造成混淆，但我仍然建议更改迭代变量名称。

@Green Cloak Guy 已经给出了答案，但可以使用list comprehension 即兴创作。它还有助于使用比list 稍少的内存，更少的行数和更少的时间消耗。我建议numpy 使用array，但让我们离开吧。

print([f'{packs * prices[0]:.2f}' if packs < 35 else f'{(int(math.floor(packs / 36)) * prices[1]) + ((packs % 36) * prices[0]):.2f}' for packs in packs_purchased])

输出：

>>> [42.50, 25.50, 125.00]

上面的输出称为list，而不是您在所需输出中声明的内容。 如果你想要那个输出，你可以做，就像@Green Cloak Guy 所做的那样，但这里仍然是一个例子：

CREATED_LIST = [f'{packs * prices[0]:.2f}' if packs < 35 else f'{(int(math.floor(packs / 36)) * prices[1]) + ((packs % 36) * prices[0]):.2f}' for packs in packs_purchased]
print(f'packs_spent({", ".join(CREATED_LIST)})')

输出：

>>> packs_spent(42.50, 25.50, 125.00)

Answer 4

import math
packs_purchased = (10, 6, 36)
dice_purchased = (2, 0, 1)
board_games_purchased = (3, 2, 0)
prices = (4.25, 125, 11, 50)

result = []
for packs_purchased in packs_purchased:
    if packs_purchased < 35:
        packs_spent = packs_purchased * prices[0]
    else:
        packs_spent = (int(math.floor(packs_purchased / 36)) * prices[1]) + ((packs_purchased % 36) * prices[0])
    a = ("%.2f" % packs_spent)
    result.append(a)
    
result = list(map(float, result))
print("packs_spent:", (result))