与python列表混淆：它们还是不是迭代器？ [英] Confused with python lists: are they or are they not iterators?

问题描述

我正在学习 Alex Marteli的Python in a Nutshell ，书中暗示任何具有<$的对象c $ c> next（）方法是（或至少可以用作）迭代器。它还建议大多数迭代器是通过对名为 iter 的方法的隐式或显式调用构建的。

I am studying Alex Marteli's Python in a Nutshell and the book suggests that any object that has a next() method is (or at least can be used as) an iterator. It also suggests that most iterators are built by implicit or explicit calls to a method called iter.

阅读本文后在书中，我感受到了尝试它的冲动。我启动了一个python 2.7.3解释器并执行了此操作：

After reading this in the book, I felt the urge to try it. I fired up a python 2.7.3 interpreter and did this:

>>> x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> for number in range(0, 10):
...     print x.next()

然而结果如下：

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
AttributeError: 'list' object has no attribute 'next'

在混乱中，我试过通过 dir（x）来研究x对象的结构，我注意到它有一个 __ iter __ 函数对象。所以我发现它可以用作迭代器，只要它支持那种类型的接口。

In confusion, I tried to study the structure of the x object via dir(x) and I noticed that it had a __iter__ function object. So I figured out that it can be used as an iterator, so long as it supports that type of interface.

所以当我再次尝试时，这次略有不同，尝试要做到这一点：

So when I tried again, this time slightly differently, attempting to do this:

>>> _temp_iter = next(x)

我收到此错误：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list object is not an iterator

但是如何才能将列表作为迭代器，因为它似乎支持这个界面，并且当然可以在以下上下文中使用：

But how can a list NOT be an iterator, since it appears to support this interface, and can be certainly used as one in the following context:

>>> for number in x:
...     print x

有人可以帮我吗在我的脑海中澄清这一点？

推荐答案

它们是 iterable ，但它们不是迭代。可以将它们传递给 iter（），以隐式（或者通过 for ）或显式获取它们的迭代器，但它们本身并不是迭代器。

They are iterable, but they are not iterators. They can be passed to iter() to get an iterator for them either implicitly (e.g. via for) or explicitly, but they are not iterators in and of themselves.

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