[FIXED] How to use asynchronous coroutines like a generator?

Issue

I want develop a web-socket watcher in python in such a way that when I send sth then it should wait until the response is received (sort of like blocking socket programming) I know it is weird, basically I want to make a command line python 3.6 tool that can communicate with the server WHILE KEEPING THE SAME CONNECTION LIVE for all the commands coming from user.

I can see that the below snippet is pretty typical using python 3.6.

import asyncio
import websockets
import json
import traceback

async def call_api(msg):
   async with websockets.connect('wss://echo.websocket.org') as websocket:
       await websocket.send(msg)
       while websocket.open:
           response = await websocket.recv()
           return (response)

print(asyncio.get_event_loop().run_until_complete(call_api("test 1")))

print(asyncio.get_event_loop().run_until_complete(call_api("test 2")))

but this will creates a new ws connection for every command which defeats the purpose. One might say, you gotta use the async handler but I don't know how to synchronize the ws response with the user input from command prompt.

I am thinking if I could make the async coroutine (call_api) work like a generator where it has yield statement instead of return then I probably could do sth like beow:

async def call_api(msg):
   async with websockets.connect('wss://echo.websocket.org') as websocket:
       await websocket.send(msg)
       while websocket.open:
           response = await websocket.recv()
           msg = yield (response)

generator = call_api("cmd1")

cmd  = input(">>>")

while cmd != 'exit'
    result = next(generator.send(cmd))
    print(result)
    cmd  = input(">>>")

Please let me know your valuable comments.

Thank you

Solution

This can be achieved using an asynchronous generator (PEP 525).

Here is a working example:

import random
import asyncio


async def accumulate(x=0):
    while True:
        x += yield x
        await asyncio.sleep(1)


async def main():
    # Initialize
    agen = accumulate()
    await agen.asend(None)
    # Accumulate random values
    while True:
        value = random.randrange(5)
        print(await agen.asend(value))


asyncio.run(main())

Answered By - Vincent