On Tue, Sep 6, 2016 at 9:27 AM, Sven R. Kunze <srku...@mail.de> wrote:
> Hi Yury,
>
> just for my understanding:
>
> On 04.09.2016 01:31, Yury Selivanov wrote:
>>
>> We propose to allow the use of ``await`` expressions in both
>> asynchronous and synchronous comprehensions::
>>
>> result = [await fun() for fun in funcs]
>> result = {await fun() for fun in funcs}
>> result = {fun: await fun() for fun in funcs}
>>
>
> This will produce normal lists, sets and dicts, right?
>
> Whereas the following will produce some sort of async lists, sets, and
> dicts?
>
>> result = [await fun() async for fun in funcs]
>> result = {await fun() async for fun in funcs}
>> result = {fun: await fun() async for fun in funcs}
>
>
> If so, how do I read values from an async list/set/dict?
AIUI they won't return "async lists" etc; what they'll do is
asynchronously return list/set/dict. Imagine an async database query
that returns Customer objects. You could get their names thus:
names = [cust.name async for cust in find_customers()]
And you could enumerate their invoices (another database query) with a
double-async comprehension:
invoices = {cust.name: await cust.list_invoices() async for cust in
find_customers()}
As always, you can unroll a comprehension to the equivalent statement form.
_tmp = {}
async for cust in find_customers():
_tmp[cust.name] = await cust.list_invoices()
invoices = _tmp
or with the original example:
_tmp = []
async for fun in funcs:
_tmp.append(await fun())
result = _tmp
Hope that helps.
ChrisA
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