我正在研究 Alex Marteli 的 Python 简述 并且本书建议任何具有 next()
方法的对象都是(或至少可以用作)迭代器.它还表明,大多数迭代器是通过对名为 iter
的方法的隐式或显式调用来构建的.
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
.
读完这本书后,我有一种尝试的冲动.我启动了一个 python 2.7.3 解释器并这样做了:
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()
然而结果是这样的:
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
AttributeError: 'list' object has no attribute 'next'
在困惑中,我试图通过 dir(x)
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,尝试这样做:
So when I tried again, this time slightly differently, attempting to do this:
>>> _temp_iter = next(x)
我收到了这个错误:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: list object is not an iterator
但是列表怎么可能不是迭代器,因为它似乎支持此接口,并且在以下上下文中肯定可以用作一个:
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
有人可以帮我澄清一下吗?
它们是可迭代的,但它们不是迭代器.它们可以被传递给 iter()
以隐式地(例如通过 for
)或显式地为它们获取迭代器,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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