On Sat, Jan 18, 2014 at 4:22 AM, Chris “Kwpolska” Warrick
<kwpol...@gmail.com> wrote:
> For Python 2, use xrange() instead to get an iterator. In Python 3,
> range() is already an iterator.
`xrange` and 3.x `range` aren't iterators. They're sequences. A
sequence implements `__len__` and `__getitem__`, which can be used to
implement an iterator, reversed iterator, and the `in` operator (i.e.
`__contains__`).
class Sequence:
def __len__(self):
return 3
def __getitem__(self, k):
if k > 2:
raise IndexError
return k
>>> seq = Sequence()
>>> len(seq)
3
>>> type(iter(seq))
<class 'iterator'>
>>> list(seq)
[0, 1, 2]
>>> type(reversed(seq))
<class 'reversed'>
>>> list(reversed(seq))
[2, 1, 0]
>>> 0 in seq
True
>>> 3 in seq
False
`xrange` and Py3 `range` both implement the following special methods:
__len__
__getitem__
__iter__
__reversed__
3.x `range` also implements:
__contains__
index
count
Neither supports sequence concatenation or repetition. Both are
manually registered as a subclass of the abstract class
`collections.Sequence`.
>>> issubclass(range, collections.Sequence)
True
http://docs.python.org/3/library/collections.abc
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