[Python-Dev] Importance of "async" keyword

[Sven R. Kunze]

On 25.06.2015 21:11, Andrew Svetlov wrote:
>> Another issue that bothers me, is code reuse. Independent from whether the
>> 'async def' makes sense or not, it would not allow us to reuse asyncio
>> functions as if they were normal functions and vice versa (if I understood
>> that correctly). So, we would have to implement things twice for the asyncio
>> world and the classic world. To me, it would be important to use one
>> function in either world where it suits me better. I am uncertain if that
>> makes sense but right now it does to me.
>
> Yes, you cannot call async function from synchronous code. There are
> two worlds: classic and async.

My point is: why does everyone assume that it has to be like that?


@Nick
Thanks for these links; nice reads and reflect exactly what I think 
about these topics. Btw. complex numbers basically works the same way 
(same API) as integers. I would like to see that for functions and 
awaitables as well.

Still, the general assumption is: "the sync/async split is inherent in 
the problem domain". Why? I do not see that inherent split.


@Greg
I do not like wrappers IF it is just because to have wrappers. We 
already have 2 types of wrappers: [normal function call] and [function 
call using await]. Both works like wrappers right in the place where you 
need them.


@Steven
 > Where would the function suspend
 > if there are zero suspension points?

It would not.

 > How can you tell what the suspension
 > points *in* the coroutine are from "await func()"?

Let me answer this with a question: How can you tell what the suspension 
points *in* the coroutine are from "async def"?

 > Can you show a code snippet of your proposal?
By analogy to PEP 0492:

def complex_calc(a):
     if a >= 0:
         return await open(unicode(a)).read()
     l = await complex_calc(a - 1)
     r = complex_calc(a - 2)
     return l + '; ' + r

def business():
     return complex_calc(5)

def business_new()
     return await complex_calc(10)


Maybe, I completely missed the point of the proposal, but this is the 
way I would expect it to work. Putting in an 'await' whenever I see fit 
and it just works.


Regards,
Sven

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