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Re: generator/coroutine terminology

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Date Sun, 15 Mar 2015 13:02:33 +1100
Subject Re: generator/coroutine terminology
From Chris Angelico <rosuav@gmail.com>
Cc "python-list@python.org" <python-list@python.org>
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On Sun, Mar 15, 2015 at 11:48 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
> Chris Angelico <rosuav@gmail.com>:
>
>> On Sun, Mar 15, 2015 at 11:15 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
>>> What features do generator iterators provide on top of generic
>>> iterators?
>>
>> You can send values into them, throw exceptions into them, and close
>> them (which is a special case of the latter).
>
> Hm. I wonder why the distinction was made. IOW, why is
>
>    iter([1, 2, 3])
>
> not equivalent with
>
>    (x for x in [1, 2, 3])
>
> I can close the latter but not the former.

You don't need to close the former.

> After all,
>
>    yield from [1, 2, 3]
>
> works all right.

That's using it as an iterable, which is not quite the same as an
iterator. (Iterators are themselves iterable; iter(x) is x, for any
iterator.) What you're doing there is roughly equivalent to:

for x in [1, 2, 3]:
    yield x

but with a bunch of other simplifications and guarantees for edge
cases and things. So it's going to call iter() on what you give it.

If you treat things as iterators, you can use all sorts of things. You
don't need to distinguish the different types. The distinction is
important if you want to do more than just iterate over something.

>>> def gather():
    lst = []
    try:
      while True:
        lst.append((yield len(lst)))
    except StopIteration:
      yield lst

>>> n = gather()
>>> next(n)
0
>>> n.send("Hello")
1
>>> n.send("World")
2
>>> n.throw(StopIteration)
['Hello', 'World']

You can't do that with a simple iterator. (Not that I'm saying this is
good design...)

ChrisA

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Thread

generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-12 06:35 -0700
  Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-13 00:55 +1100
  Re: generator/coroutine terminology breamoreboy@gmail.com - 2015-03-12 06:57 -0700
  Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-13 03:27 +1100
    Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-12 09:52 -0700
      Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-12 19:55 +0200
        Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-12 19:23 -0700
          Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-13 14:30 +1100
            Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-12 22:28 -0700
              Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-13 19:23 +1100
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-13 02:12 -0700
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-13 11:36 +0200
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-14 17:04 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-14 09:54 +0200
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-14 08:04 +0000
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-14 10:30 +0200
                Re: generator/coroutine terminology Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-14 14:14 -0600
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-14 21:15 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-14 20:31 +0000
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-14 08:29 -0700
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 02:56 +1100
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-14 08:59 -0700
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 03:14 +1100
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-14 09:33 -0700
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 03:51 +1100
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-14 10:17 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-14 16:56 +0000
                Re: generator/coroutine terminology Dave Angel <davea@davea.name> - 2015-03-14 13:07 -0400
                Re: generator/coroutine terminology albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-31 12:57 +0000
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-15 19:37 +1100
                Re: generator/coroutine terminology CHIN Dihedral <dihedral88888@gmail.com> - 2015-04-18 11:07 -0700
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-13 22:32 +1100
      Re: generator/coroutine terminology Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-03-14 22:02 +0000
        Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-15 00:15 +0200
          Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 09:24 +1100
            Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-15 02:15 +0200
              Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 11:22 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-15 02:48 +0200
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-15 13:02 +1100
              Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-16 12:03 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 09:12 +0200
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-16 18:21 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 09:40 +0200
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-16 22:59 +1100
                Re: generator/coroutine terminology Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-16 01:37 -0600
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 09:52 +0200
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-16 23:02 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 14:42 +0200
                Re: generator/coroutine terminology Jonas Wielicki <jonas@wielicki.name> - 2015-03-16 13:39 +0100
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-16 19:36 +1100
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-16 19:58 +1100
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-16 22:51 +1100
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-03-17 00:16 +1100
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 14:32 +0200
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 05:51 -0700
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 15:13 +0200
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-17 01:32 +1100
                Re: generator/coroutine terminology Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-16 08:45 -0600
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-17 00:39 +1100
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 07:19 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-16 14:26 +0000
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 07:37 -0700
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 07:55 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-16 18:19 +0000
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 19:52 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-17 03:07 +0000
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 20:18 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-17 03:25 +0000
                Re: generator/coroutine terminology Rustom Mody <rustompmody@gmail.com> - 2015-03-16 20:33 -0700
                Re: generator/coroutine terminology Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-17 03:55 +0000
                Re: generator/coroutine terminology Mario Figueiredo <marfig@gmail.com> - 2015-03-17 04:22 +0100
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-17 01:35 +1100
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-17 01:36 +1100
                Re: generator/coroutine terminology Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-16 08:52 -0600
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 17:09 +0200
                Re: generator/coroutine terminology Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-16 09:26 -0600
                Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-16 18:05 +0200
                Re: generator/coroutine terminology albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-31 13:18 +0000
                Re: generator/coroutine terminology Dave Angel <davea@davea.name> - 2015-03-31 09:38 -0400
                Re: generator/coroutine terminology albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-31 15:03 +0000
                Re: generator/coroutine terminology Chris Angelico <rosuav@gmail.com> - 2015-04-01 02:36 +1100
                Re: generator/coroutine terminology Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-03 17:02 +1100
                Re: generator/coroutine terminology albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-18 17:52 +0000
                Re: generator/coroutine terminology Paul Rubin <no.email@nospam.invalid> - 2015-04-02 23:46 -0700
  Re: generator/coroutine terminology Terry Reedy <tjreedy@udel.edu> - 2015-03-12 16:11 -0400
    Re: generator/coroutine terminology Marko Rauhamaa <marko@pacujo.net> - 2015-03-12 22:22 +0200

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