Question

我很困惑tee()真的如何运作。

l = [1, 2, 3, 4, 5, 6]
iterators3 = itertools.tee(l, 3)
for i in iterators3:
    print (list(i))

输出：

[1, 2, 3, 4, 5, 6]
[1, 2, 3, 4, 5, 6]
[1, 2, 3, 4, 5, 6]

这没关系。但如果我尝试：

a, b, c = itertools.tee(l)

我收到此错误：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not enough values to unpack (expected 3, got 2)

为什么？

Answer 1

tee有2个参数，一个迭代器和一个数字，它会复制实际的迭代器（带有他的上下文）你作为参数传递的次数，所以你实际上不能解开比tee更多的生成器创建：

a,b = tee(l) #this is ok, since it just duplicate it so you got 2 
a,b,c = tee(l, 3) #this is also ok, you will get 3 so you can unpack 3
a,b = tee(l, 3) #this will fail, tee is generating 3 but you are trying to unpack just 2 so he dont know how to unpack them

在python 3中，您可以像这样解压缩：

a, *b = tee(l, 3)

其中a将保存来自tee的第一个迭代器，而b将其余的迭代器保存在列表中。

itertools tee（）迭代器拆分

1 个答案: