Public API

class cl.loop.Loop(*futures, loop=None, return_exceptions=False)

Asyncio Event loop context manager.

Context manager which get existing event loop or if none exist will create new one.

All coroutines are converted to task and scheduled to execute in near future. Scheduling is safe for long running tasks.

Example:

Create coroutine using @asyncio.coroutine decorator or with async/await syntax

>>> async def wait_for_it(timeout):
...     await asyncio.sleep(timeout)
...     return 'success sleep for {} seconds'.format(timeout)
...

Use context manager to get result from one or more coroutines

>>> with Loop(wait_for_it(5), wait_for_it(3), return_exceptions=True) as loop:
...     result = loop.run_until_complete()
...
>>> result
['success sleep for 3 seconds', 'success sleep for 5 seconds']

When single coroutine has been scheduled to run, only single value will be returned.

>>> with Loop(wait_for_it(4)) as loop:
...     result = loop.run_until_complete()
...
>>> result
'success sleep for 4 seconds'

Parameters:

• futures (asyncio.Future, asyncio.coroutine) – One or more coroutine or future.
• loop (asyncio.AbstractEventLoop) – Optional existing loop.
• return_exceptions (Boolean) – If True will return exceptions as result.
• stop_when_done (Boolean) – If True will close the loop on context exit.

futures = None

Gathered futures.

gather(*futures: typing.Union[asyncio.futures.Future, <function coroutine at 0x7f4ce4966620>])

Gather list of futures/coros and return single Task ready to schedule.

Example:

Prepare all futures to execution

>>> async def do_something():
...     return 'something'
...
>>> async def do_something_else():
...     return 'something_else'
...

Gather all tasks and then pass to context loop

>>> loop = Loop(return_exceptions=True)
>>> loop.gather(do_something(), do_something_else())
>>> with loop as l:
...     result = l.run_until_complete()
...

Parameters:futures (asyncio.Future, asyncio.coroutine) – One or more coroutine or future. Returns:Futures grouped into single future Return type:asyncio.Task, asyncio.Future

run_until_complete()

Run loop until all futures are done.

Schedule futures for execution and wait until all are done. Return value from future, or list of values if multiple futures had been passed to constructor or gather method.

All results will be in the same order as order of futures passed to constructor.

Example:

>>> async def slow():
...     await ultra_slow_task()
...     return 'ultra slow'
...
>>> async def fast():
...     await the_fastest_task_on_earth()
...
>>> with Loop(slow(), fast()) as loop:
...     result = loop.run_until_complete()
...
>>> result
['ultra slow', None]

Returns:Value from future or list of values. Return type:None, list, Any

cancel()

Cancel pending futures.

If any of futures are already done its result will be lost. Result of loop execution will be None.

Example:

>>> async def nuke_loop():
...     loop.cancel()
...
>>> loop = Loop()
>>> loop.gather(nuke_loop())
>>> with loop as lo:
...     result = lo.run_until_complete()
...
>>> result
None