[docs] [issue33117] asyncio example uses non-existing/documented method

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan <tir.karthi at gmail.com> added the comment:

I think `asyncio.run_coroutine_threadsafe(coro, loop)` returns a concurrent.futures.Future [1] which supports timeout and not asyncio.Future which doesn't support timeout. Please add in if I am missing anything. Since asyncio docs are being rewritten this would be a great time to contribute too if you would like to add more clarification.

Docs at [1] also say the below : 

asyncio.run_coroutine_threadsafe(coro, loop)

    Submit a coroutine to the given event loop. Thread-safe.

    Return a concurrent.futures.Future to wait for the result from another OS thread.


```
# bpo33117.py. This needs to be called from a different thread as docs said but I am using future.result(timeout) just to make sure there is no error with respect to function argument.

import asyncio

loop = asyncio.get_event_loop()
timeout = 4

# Create a coroutine
coro = asyncio.sleep(1, result=3)

# Submit the coroutine to a given loop
future = asyncio.run_coroutine_threadsafe(coro, loop)

# Wait for the result with an optional timeout argument
assert future.result(timeout) == 3
```


➜  cpython git:(master) ./python.exe bpo33117.py
Traceback (most recent call last):
  File "../bpo33117.py", line 13, in <module>
    assert future.result(timeout) == 3
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/concurrent/futures/_base.py", line 438, in result
    raise TimeoutError()
concurrent.futures._base.TimeoutError

[1] https://docs.python.org/3.8/library/concurrent.futures.html#concurrent.futures.Future



Thanks

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nosy: +xtreak

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<https://bugs.python.org/issue33117>
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