It doesn't behave like a generator because it doesn't implement send, throw, or close. It's a sequence because it implements: __getitem__, __len__ __contains__, __iter__, __reversed__, index, and count.
On 30.09.2015 20:26, Andrew Barnert via Python-ideas wrote:
> On Sep 30, 2015, at 11:11, M.-A. Lemburg <mal@egenix.com> wrote:
>>
>>> On 30.09.2015 19:19, Neil Girdhar wrote:
>>> I guess, I'm just asking for enumerate to go through the same change that
>>> range went through. Why wasn't it a problem for range?
>>
>> range() returns a list in Python 2 and a generator in Python 3.
>
> No it doesn't. It returns a (lazy) sequence. Not a generator, or any other kind of iterator.
You are right that it's not of a generator type
and more like a lazy sequence. To be exact, it returns
a range object and does implement the iter protocol via
a range_iterator object.
In Python 2 we have the xrange object which has similar
properties, but not the same, e.g. you can't slice it.
> I don't know why so many people seem to believe it returns a generator. (And, when you point out what it returns, most of them say, "Why was that changed from 2.x xrange, which returned a generator?" but xrange never returned a generator either--it returned a lazy almost-a-sequence from the start.)
Perhaps because it behaves like one ? :-)
Unlike an iterator, it doesn't iterate over a sequence, but instead
generates the values on the fly.
FWIW: I don't think many people use the lazy sequence features
of range(), e.g. the slicing or index support. By far most
uses are in for-loops.
--
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