Mailman 3 Allow return value in asynchronous generator - Python-ideas

26 Dec 2020


      Currently, asynchronous generators don't allow a non-empty `return` statement:
```python
import asyncio
async def async_generator():
    x = yield 1
    await asyncio.sleep(1)
    if x:
        ...
        return "result A"  # SyntaxError
    else:
        ...
        return "result B"
```
unlike regular generators which communicate their return value via the `value` attribute on the `StopIteration` exception:
```python
def synchronous_generator():
    x = yield 1
    if x:
        ...
        return "result A"   # raises StopIteration with value="result A"
    else:
        ...
        return "result B"
```
I think that `StopAsyncIteration` should behave likewise and have a `value` attribute containing the return value. I'm not aware of any reason to maintain this asymmetry.