2014-11-27 20:06 GMT+01:00 Guido van Rossum <gu...@python.org>:
> The issue here is that asyncio only interprets StopIteration as returning
> from the generator (with a possible value),
I'm not sure that the issue is directly related to asyncio.
trollius_coro() raises a StopIteration to return the result to caller.
To caller is "result = yield from coro", it's not the complex
Task._step() method. So it's pure Python, except if I missed
something.
> The only way out I can think of is to have asyncio special-case the Return
> exception -- we could do that by defining a new exception (e.g.
> AlternateReturn) in asyncio that gets treated the same way as StopIteration,
> so that Trollius can inherit from AlternateReturn (if it exists).
I don't see how it would work.
Here is a simplified example of my issue. You need to modify all
"yield from coro" to write instead "yield from catch_return(coro)", or
I missed something important.
---
PEP479 = True
if not PEP479:
# trollius: no need for catch_return() before the PEP 479
class Return(StopIteration):
pass
else:
# PEP 479: need catch_return()
class Return(Exception):
def __init__(self, value):
self.value = value
def return_value(value):
if 0:
yield
raise Return(value)
def catch_return(gen):
try:
value = (yield from gen)
except Return as exc:
return exc.value
def add_one(gen):
value = (yield from gen)
return value + 1
def consume_generator(gen):
while True:
try:
next(gen)
except StopIteration as exc:
return exc.value
gen1 = return_value(3)
if PEP479:
gen1 = catch_return(gen1)
gen2 = add_one(gen1)
print(consume_generator(gen2))
---
Victor
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