A tiny python asyncio just for learning 🙋‍♂️, document below is my personal notes during the learning, may change frequently.

I implement a series of TCP echo server for the test of tiny-asyncio client including multi threading, IO multiplexing and so on. Details can be found here.

Event loop is just a while True loop, the basic functionality of event loop is to keep find out which functions can be executed and execute them. Event loop's implementation I think is not related to coroutine or generator, it's just a scheduler used to execute functions (even regardless their return value).

The core code in Future

def __await__(self):
    yield self


__iter__ = __await__

yield itself. and Task's __step will receive bottom future object, and add done callback to them. Notice that all function will be executed by a global event loop including __step. I think this part is the core part in asyncio.

What eventually block the program in python design is the yield, while yield from (await) just keep send None to generator (or we call coroutine) unless got a StopIteration, and

x = yield from coro

StopIteration's value will be assigned to x, notice that if we call return in generator or coroutine function it will raise a StopIteration.

official python selectors module

• get_event_loop
• selectors block
• async sock
• gather
• exception handle, may with bug 🤔
• creat server
• cancel

• cpython