在python 3中重用zip迭代器 [英] Re-using zip iterator in python 3

问题描述

我有 zip 对象：

L_RANGES = zip(range(10, 20), range(11, 21))

首次调用 L_RANGES 没问题：

print(type(L_RANGES))
for a, b in L_RANGES:
  print(a, b)

输出：

<class 'zip'>
10 11
11 12
12 13
13 14
14 15
15 16
16 17
17 18
18 19
19 20

接下来的电话不显示任何内容。有没有办法维护或重置它。到目前为止我可以将其转换为列表：

Bu the next calls do not display anything. Is there any way to maintain or reset that. So far I can just convert it to the list:

L_RANGES = list(zip(range(10, 20), range(11, 21)))

推荐答案

如果你要创造每次循环时都会生成一个生成器，它可以解决所有问题，因为您可以多次重复使用它。为此，将 L_RANGES 从简单生成器转换为 lambda 创建生成器，但不要忘记调用每次使用（）：

If you were to create a generator each time you loop, that would solve everything, because you could reuse that multiple times. For that, convert L_RANGES from a simple generator to a lambda creating generators, but don't forget to "call" it each time with ():

L_RANGES = lambda: zip(range(10, 20), range(11, 21))

for a, b in L_RANGES():
  print(a, b)

for a, b in L_RANGES():
  print(a, b)

#works as many times as you want

与其他答案相比，这不占用内存（这是转换为列表的缺点），并且每次要循环时不需要多个变量（通过使用 tee ）这使得这种方式更加灵活（如果需要，您可以迭代1000次，而无需创建 L_RANGES_1 ... L_RANGES_999 ）例如：

Compared to the other answers this doesn't take up memory (which is the downside of converting to a list) and doesn't require multiple variables for each time you want to loop (by using tee) which makes this way more flexible (you can iterate 1000 times if necessary, without creating L_RANGES_1...L_RANGES_999) for example:

for i in range(1000):
    for a, b in L_RANGES():
        print(a, b)

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