python – 从生成器创建迭代器返回相同的对象

return self

从docs

The iterator objects themselves are required to support the following
two methods,which together form the iterator protocol:

iterator.__iter__() Return the iterator object itself. This is
required to allow both containers and iterators to be used with the
for and in statements. This method corresponds to the tp_iter slot of
the type structure for Python objects in the Python/C API.

iterator.__next__() Return the next item from the container. If there
are no further items,raise the StopIteration exception. This method
corresponds to the tp_iternext slot of the type structure for Python
objects in the Python/C API.

所以,考虑一个迭代器的另一个例子：

>>> x = [1,5]
>>> it = iter(x)
>>> it2 = iter(it)
>>> next(it)
1
>>> next(it2)
2
>>> it is it2
True

所以,同样,列表是可迭代的,因为它有一个返回迭代器的__iter__方法.这个迭代器也有一个__iter__方法,它应该总是返回自己,但它也有一个__next__方法.

所以,考虑一下：

>>> x = [1,5]
>>> it = iter(x)
>>> hasattr(x,'__iter__')
True
>>> hasattr(x,'__next__')
False
>>> hasattr(it,'__iter__')
True
>>> hasattr(it,'__next__')
True
>>> next(it)
1
>>> next(x)
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
TypeError: 'list' object is not an iterator

对于发电机：

>>> g = (x**2 for x in range(10))
>>> g
<generator object <genexpr> at 0x104104390>
>>> hasattr(g,'__iter__')
True
>>> hasattr(g,'__next__')
True
>>> next(g)
0

现在,您正在使用生成器表达式.但你可以使用生成器功能.完成您正在做的事情最直接的方法就是使用：

def paired(data):
    for e in data:
        yield (e,2*e)

然后使用：

it1 = paired(data)
it2 = paired(data)

在这种情况下,it1和it2将是两个独立的迭代器对象.