call_magic_method.py

"""
This snippet illustrates the usage of the __call__() magic method, how it can be used to solve a real problem.
Please read code comments for further details.
"""
import asyncio

import binance
from autobahn.asyncio import WebSocketClientProtocol, WebSocketClientFactory


# noinspection PyPep8Naming
class WsClientProtocol(WebSocketClientProtocol):
    name: str
    arg2: float

    def __init__(self, name: str, arg2: float):
        super().__init__()
        self.name = name
        self.arg2 = arg2

    def onMessage(self, payload, isBinary):
        if isBinary:
            print(f"{self.name} onMessage Binary: {len(payload)} bytes received")
        else:
            print(f'{self.name} onMessage {payload}')

    def onOpen(self):
        print(f'{self.name} - Connection Opened')

    def __call__(self, *args, **kwargs):
        # __call__ is a magic method called when something is treated as callable (by using ()), for
        # example self.onOpen is callable, because we can use () -> self.onOpen()
        # to make an instance of this class callable we implement __call__() like we do here.
        # This method will be called by the framework to create an object, we just return ourselves (self)
        # as the object.
        return self


loop = asyncio.get_event_loop()
endpoint = f"wss://stream.binance.com:9443/ws/btcusdt@kline_{binance.Client.KLINE_INTERVAL_1MINUTE}"

factory = WebSocketClientFactory(endpoint)
# protocol field must be a callable object
# since we don't want to provide the class as protocol field
# because it would create one object of such class but without giving us
# the opportunity to pass arguments, then we create an object ourselves, passing all
# arguments we want, and implementing the __call__ so when it is called by autobahn
# framework, we return the instance we already created ourselves
factory.protocol = WsClientProtocol('task1-controller', 3.0)
coroutine = loop.create_connection(factory, "stream.binance.com", 9443, ssl=True)
loop.run_until_complete(coroutine)
loop.run_forever()
loop.close()