Thank you Elvis for the documentation! Cancellation is one of the most complex part of asynchronous programming, and I don't think that asyncio documentation explains it properly. We may document the behaviour on cancellation for most task functions.

https://docs.python.org/dev/library/asyncio-task.html#task-functions

as_completed() behaviour on cancellation is not documented for example.

The wait() documentation should be backported to 3.6 as well.