AsyncIO
AsyncIO is the current state of the art in Python concurrent programming. It combines the concept of futures and an event loop with coroutines. The result is about as elegant and easy to understand as it is possible to get when writing responsive applications that don't seem to waste time waiting for input.
For the purposes of working with Python's async features, a coroutine is a function that is waiting for an event, and also can provide events to other coroutines. In Python, we implement coroutines using async def. A function with async must work in the context of an event loop which switches control among the coroutines waiting for events. We'll see a few Python constructs using await expressions to show where the event loop can switch to another async function.
It's crucial to recognize that async operations are interleaved, and not – generally – parallel. At most one coroutine is in control and processing, and all the others...