如何调用类中包含的异步函数? [英] How to call a async function contained in a class?

问题描述

基于 这个答案，我想在从另一个文件导入的类中构建一个异步 websoket 客户端:

Based on this answer I want to build an async websoket client in a class which would be imported from another file:

#!/usr/bin/env python3

import sys, json
import asyncio
from websockets import connect

class EchoWebsocket:
    def __await__(self):
        # see: https://stackoverflow.com/a/33420721/1113207
        return self._async_init().__await__()

    async def _async_init(self):
        self._conn = connect('wss://ws.binaryws.com/websockets/v3')
        self.websocket = await self._conn.__aenter__()
        return self

    async def close(self):
        await self._conn.__aexit__(*sys.exc_info())

    async def send(self, message):
        await self.websocket.send(message)

    async def receive(self):
        return await self.websocket.recv()

class mtest:
    async def start(self):
        try:
            self.wws = await EchoWebsocket()
        finally:
            await self.wws.close()

    async def get_ticks(self):
        await self.wws.send(json.dumps({'ticks_history': 'R_50', 'end': 'latest', 'count': 1}))
        return await self.wws.receive()

if __name__ == '__main__':
    a = mtest()
    loop = asyncio.get_event_loop()
    loop.run_until_complete(a.start())

我将它导入到 main.py 中，在那里我有以下内容:

And I import it in main.py, where I have the following:

from testws import *

a = mtest()
print (a.get_ticks())
print ("this will be printed after the ticks")

但它检索我以下错误:

root@ubupc1:/home/dinocob# python3 test.py
<coroutine object hello.get_ticks at 0x7f13190a9200>
test.py:42: RuntimeWarning: coroutine 'mtest.get_ticks' was never awaited
  print (a.get_ticks())
this will be printed after the ticks

这是怎么回事?如果在 def 的开头有 async 字，为什么我无法访问 mtest.get_ticks?

What's is going on here? Why I'm not able to access mtest.get_ticks if it has the async word at the begining of def?

推荐答案

我终于找到了正确的方法(特别感谢 @dirn)

Finally I could find the right way to do it (special thanks to @dirn)

#!/usr/bin/env python3

import sys, json
import asyncio
from websockets import connect

class EchoWebsocket:
    async def __aenter__(self):
        self._conn = connect('wss://ws.binaryws.com/websockets/v3')
        self.websocket = await self._conn.__aenter__()        
        return self

    async def __aexit__(self, *args, **kwargs):
        await self._conn.__aexit__(*args, **kwargs)

    async def send(self, message):
        await self.websocket.send(message)

    async def receive(self):
        return await self.websocket.recv()

class mtest:
    def __init__(self):
        self.wws = EchoWebsocket()
        self.loop = asyncio.get_event_loop()

    def get_ticks(self):
        return self.loop.run_until_complete(self.__async__get_ticks())

    async def __async__get_ticks(self):
        async with self.wws as echo:
            await echo.send(json.dumps({'ticks_history': 'R_50', 'end': 'latest', 'count': 1}))
            return await echo.receive()

在 main.py 中:

And this in main.py:

from testws import *

a = mtest()

foo = a.get_ticks()
print (foo)

print ("async works like a charm!")

foo = a.get_ticks()
print (foo)

这是输出:

root@ubupc1:/home/dinocob# python3 test.py
{"count": 1, "end": "latest", "ticks_history": "R_50"}
async works like a charm!
{"count": 1, "end": "latest", "ticks_history": "R_50"}

欢迎任何改进它的提示！;)

Any tip to improve it is welcomed! ;)

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