如何正确使用龙卷风异步

Question

在 tornado 的文档中提到 gen.coroutine 装饰器来自旧版本。较新的应该与aysnc一起使用。到目前为止，我未能为 Tornado 6.0.3 转换那段小代码。

import tornado.web
import tornado.websocket
import tornado.httpserver

from random import randint
from tornado import gen
from tornado.ioloop import IOLoop

from web_handlers import HandlerIndexPage
from web_handlers import HandlerWebSocket

msg = 'none'

@gen.coroutine
def generate_random_int():
    global msg
    while True:
        msg = str(randint(0, 100))
        print('generated:', msg)
        yield gen.sleep(1.0)

@gen.coroutine
def generate_message_to_sockets():
    global msg
    while True:
        print ('new messageToCon: ', msg)
        yield [con.write_message(msg) for con in HandlerWebSocket.connections]
        yield gen.sleep(1.0)


class webApplication(tornado.web.Application):
    def __init__(self):
        handlers = [
            (r'/', HandlerIndexPage),
            (r'/websocket', HandlerWebSocket)
        ]

        settings = {
            'template_path': 'templates'
        }
        tornado.web.Application.__init__(self, handlers, **settings)

if __name__ == '__main__':
    ws_app = webApplication()
    server = tornado.httpserver.HTTPServer(ws_app)
    port = 9090
    server.listen(port)
    print('websocket listening on port:'+ str(port))
    IOLoop.current().spawn_callback(generate_random_int)
    IOLoop.current().spawn_callback(generate_message_to_sockets)
    IOLoop.instance().start()

如何正确使用异步？

Answer 1

在 Tornado 中，协程是可以插入 Python2 的生成器，而异步函数是 Python3 中的第一个 class 公民。它们具有不同的语义（例如，您可以从异步函数 return 而不是协程）。您需要更改的代码如下所示：

...

import asyncio

...

async def generate_random_int():
    global msg
    while True:
        msg = str(randint(0, 100))
        print('generated:', msg)
        await gen.sleep(1.0)

async def generate_message_to_sockets():
    global msg
    while True:
        print ('new messageToCon: ', msg)
        futures = [con.write_message(msg) for con in HandlerWebSocket.connections]
        if futures:
            await asyncio.wait(futures)
        await gen.sleep(1.0)
...

您可以在此处查看与您的用例类似的示例：https://www.tornadoweb.org/en/stable/ioloop.html#ioloop-objects

Answer 2

Python 3.5引入了async和await关键字（使用这些关键字的函数也称为“原生协程”）。

# Decorated:                    # Native:

# Normal function declaration
# with decorator                # "async def" keywords
@gen.coroutine
def a():                        async def a():
    # "yield" all async funcs       # "await" all async funcs
    b = yield c()                   b = await c()
    # "return" and "yield"
    # cannot be mixed in
    # Python 2, so raise a
    # special exception.            # Return normally
    raise gen.Return(b)             return b

如何正确使用龙卷风异步

how to correctly use async with tornado

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