circuitpython/tests/basics/async_for.py
Jonathan Hogg 37e1b5c891 py/compile: Don't await __aiter__ special method in async-for.
MicroPython's original implementation of __aiter__ was correct for an
earlier (provisional) version of PEP492 (CPython 3.5), where __aiter__ was
an async-def function.  But that changed in the final version of PEP492 (in
CPython 3.5.2) where the function was changed to a normal one.  See
https://www.python.org/dev/peps/pep-0492/#why-aiter-does-not-return-an-awaitable
See also the note at the end of this subsection in the docs:
https://docs.python.org/3.5/reference/datamodel.html#asynchronous-iterators
And for completeness the BPO: https://bugs.python.org/issue27243

To be consistent with the Python spec as it stands today (and now that
PEP492 is final) this commit changes MicroPython's behaviour to match
CPython:  __aiter__ should return an async-iterable object, but is not
itself awaitable.

The relevant tests are updated to match.

See #6267.
2020-07-25 00:58:18 +10:00

30 lines
603 B
Python

# test basic async for execution
# example taken from PEP0492
class AsyncIteratorWrapper:
def __init__(self, obj):
print('init')
self._it = iter(obj)
def __aiter__(self):
print('aiter')
return self
async def __anext__(self):
print('anext')
try:
value = next(self._it)
except StopIteration:
raise StopAsyncIteration
return value
async def coro():
async for letter in AsyncIteratorWrapper('abc'):
print(letter)
o = coro()
try:
o.send(None)
except StopIteration:
print('finished')