ASYNC, AWAITasynchronous |eɪˈsɪŋkrənəs| (adj.) 異步的

Adrian Liaw

廖偉涵 Adrian Liawadrianliaw / adrianliaw2000http://github.com/adrianliaw

AGENDAWhat is asyncTraditional approachasyncio

PSEUDOCODEwhile not everyone is done:

person = select 1st person in the queue

if not check_homework(person):

person.fill_blanks(do go_to_queue() when done)

WHAT IS ASYNCAsynchronous I/O or non-blocking I/OSingle-threaded

Non-blocking sockets

select, epoll, kqueue

event loop"Tell me when you're done"

TRADITIONAL APPROACH

CALLBACKSfs.readFile("foo", "utf8", function (error, result) { if (!error) console.log(error); else console.log(result)});

CONS OF CALLBACKMessyHard to save stateHard to organiseBad for Python

GENERATOR

>>> def foo():... yield "foo"... yield "bar"

>>> gen = foo()

>>> gen<generator object foo>

>>> next(gen)"foo">>> next(gen)"bar"

>>> next(gen)StopIteration:

>>> def foo():... bar = yield "foo"... baz = yield bar * 10

>>> gen = foo()>>> next(gen)'foo'>>> gen.send(20)200>>> gen.throw(ValueError)ValueError:

>>> def foo():... baz = yield from bar()... print(baz)

>>> def bar():... yield 1... yield 2... return "fooooo"

PEP 3156asyncio

@asyncio.coroutinedef coro_func(): print("Sleeping...") yield from asyncio.sleep(3) print("Done")

loop = asyncio.get_event_loop()loop.run_until_complete(coro_func())

async def coro_func(): print("Sleeping...") await asyncio.sleep(3) print("Done")

loop = asyncio.get_event_loop()loop.run_until_complete(coro_func())

asyncio + aiohttp = <3Fast Scraping In Python With Asyncio

REFERENCESPEP 3156bit.ly/coroutinesDavid Beazley - Python Concurrency From the Ground Up

Q&A