TypeError：publish（）接受2個位置參數，但給出了3個

Question

因此，我正在使用MQTT Publisher，並希望創建一個pub類。 我在這里找到了類似的問題，但我不知道它如何轉化為我的問題。

這是我的代碼：

def send_on_sensor(q, topic, delay, pub):

    while q.empty is not True:
        payload = json.dumps(q.get())
        pub.publish(payload)
        time.sleep(delay)


class Pub:
    def __init__(self, MQTT_BROKER, MQTT_TOPIC):
        self.MQTT_BROKER = MQTT_BROKER
        self.MQTT_TOPIC = MQTT_TOPIC
        self.mqttc = mqtt.Client()

        self.mqttc.on_connect = self.on_connect
        self.mqttc.publish = self.publish

        # Connect automatically on the creation of the object, but disconnect manually
        self.connect()

    def on_connect(self, client, userdata, flags, rc):
        print("Connecting to {}. Connection returned result: {}".format(self.MQTT_BROKER, rc))
        self.mqttc.subscribe(self.MQTT_TOPIC)

    def publish(self, MQTT_MSG):
        self.mqttc.publish(self.MQTT_TOPIC, MQTT_MSG)

    def connect(self):
        self.mqttc.connect(self.MQTT_BROKER)

    def disconnect(self):
        self.mqttc.disconnect()

我收到此錯誤：

Exception in thread Thread-4:
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 917, in _bootstrap_inner
    self.run()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "/Users//PycharmProjects//V3_multiTops/mt_GenPub.py", line 76, in send_on_sensor
    pub.publish(payload)
  File "/Users//PycharmProjects//V3_multiTops/mt_GenPub.py", line 129, in publish
    self.mqttc.publish(self.MQTT_TOPIC, MQTT_MSG)
TypeError: publish() takes 2 positional arguments but 3 were given

這里的問題到底是什么？如何解決？

Answer 1

您要將兩個參數傳遞給publish（）：

self.mqttc.publish(self.MQTT_TOPIC, MQTT_MSG)

但是該函數被定義為僅接受一個參數（除了self ，它會自動傳遞）：

def publish(self, MQTT_MSG):

為什么要傳遞MQTT_TOPIC ？