On Fri, Jan 24, 2014 at 8:50 AM, spir <denis.s...@gmail.com> wrote:
>
> xs is an iterator (__next__ is there), then Python uses it directly, thus
> what is the point of __iter__ there? In any case, python must check whether
Python doesn't check whether a type is already an iterator. It's
simpler to require that iterators implement __iter__, like any other
non-sequence iterable. This technically allows an iterator to return a
new iterator when __iter__ is called:
class C:
def __iter__(self): return D()
def __next__(self): return 'C'
class D:
def __iter__(self): return C()
def __next__(self): return 'D'
it1 = iter(C())
it2 = iter(it1)
>>> next(it1)
'D'
>>> next(it2)
'C'
That said, it's supposed to return self.
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