[Python-Dev] semantics of subclassing things from itertools (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Thu Sep 10 10:26:08 CEST 2015

On 10.09.15 10:23, Maciej Fijalkowski wrote:

I would like to know what are the semantics if you subclass something from itertools (e.g. islice).

Right now it's allowed and people do it, which is why the documentation is incorrect. It states "equivalent to: a function-or a generator", but you can't subclass whatever it is equivalent to, which is why in PyPy we're unable to make it work in pure python. I would like some clarification on that.

There is another reason why itertools iterators can't be implemented as simple generator functions. All iterators are pickleable in 3.x.

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