Python asyncio


#!/usr/bin/env python
# WS server that sends messages at random intervals
import asyncio
import datetime
import random
import websockets
async def time(websocket, path):
    while True:
        now = datetime.datetime.utcnow().isoformat() + 'Z'
        await websocket.send(now)
        await asyncio.sleep(random.random() * 3)
start_server = websockets.serve(time, '127.0.0.1', 5678)
asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()


#!/usr/bin/env python
# WSS (WS over TLS) client example, with a self-signed certificate
import asyncio
import pathlib
import ssl
import websockets
ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
ssl_context.load_verify_locations(
    pathlib.Path(__file__).with_name('localhost.pem'))
async def hello():
    async with websockets.connect(
            'wss://localhost:8765', ssl=ssl_context) as websocket:
        name = input("What's your name? ")
        await websocket.send(name)
        print(f"> {name}")
        greeting = await websocket.recv()
        print(f"< {greeting}")
asyncio.get_event_loop().run_until_complete(hello())

这两段python使用了asyncio事件循环，本质上是一个event-loop的实现，安排任务，等待Future从而做到在单线程中的async/await语法。

这里的Future相当于js中的promise，也就是将来返回的值。

这里的run_until_complete需要一个Future对象，它会把这个参数丢进去运行。

如果是希望non-blocking，可以改用ensure_future来执行。run_until_complete会阻塞原有的线程。

# Python asyncio

Python asyncio