[Python-ideas] A send() built-in function to drive coroutines

[Luciano Ramalho]

On Mon, Feb 16, 2015 at 8:30 PM, Guido van Rossum <guido at python.org> wrote:
> This is brought up from time to time. I believe it is based on a
> misunderstanding of coroutines.

Thanks, Guido, if you could elaborate that would be great.

Meanwhile I'll try to guess what you may be referring to, please
correct me if I am wrong: the misunderstanding has to do with the fact
that between the priming next() and the first send(), the client code
should be doing something interesting. If that is not the case, then
the client code and the coroutine are not cooperating fully. Is that
it?

Best,

Luciano



>
> On Mon, Feb 16, 2015 at 4:53 AM, Luciano Ramalho <luciano at ramalho.org>
> wrote:
>>
>> Coroutines are useless until primed by a next(my_coro) call. There are
>> decorators to solve this by returning a primed coroutine. Such
>> decorators add another problem: now the user may be unsure whether a
>> specific coroutine from a third-party API should be primed or not
>> prior to use.
>>
>> How about having a built-in function named send() with the signature
>> send(coroutine, value) that does the right thing: sends a value to the
>> coroutine, priming it if necessary. So instead of writing this:
>>
>> >>> next(my_coro)
>> >>> my_coro.send(a_value)
>>
>> You could always write this:
>>
>> >>> send(my_coro, a_value)
>>
>> At a high level, the behavior of send() would be like this:
>>
>> def send(coroutine, value):
>>     if inspect.getgeneratorstate() == 'GEN_CREATED':
>>         next(coroutine)
>>     coroutine.send(value)
>>
>> Consider the above pseudo-code. Proper handling of other generator
>> states should be added.
>>
>> This would make coroutines easier to use, and would make their basic
>> usage more consistent with the usage of plain generators using a
>> function syntax -- eg. next(my_gen) -- instead of method call syntax.
>>
>> What do you think? If this has been discussed before, please send me a
>> link (I searched but came up empty).
>>
>> Best,
>>
>> Luciano
>>
>>
>>
>> --
>> Luciano Ramalho
>> Twitter: @ramalhoorg
>>
>> Professor em: http://python.pro.br
>> Twitter: @pythonprobr
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>
>
>
>
> --
> --Guido van Rossum (python.org/~guido)



-- 
Luciano Ramalho
Twitter: @ramalhoorg

Professor em: http://python.pro.br
Twitter: @pythonprobr