类型错误：on_connect（）到底需要3个参数（4给出）

问题描述：

我尝试在MQTT代理（Ubuntu的服务器）执行此代码，类型错误：on_connect（）到底需要3个参数（4给出）

当从出版商获取的数据将发送到UDP_IP。

我的代码：

import json 
import socket 
import paho.mqtt.client as mqtt 
# MQTT Settings 
MQTT_Broker = "192.168.0.106" 
MQTT_Topic = "#" 
MQTT_Port = 1883 
Keep_Alive_Interval = 45 
UDP_IP = "192.168.0.108" 
UDP_RAW_PORT = 5567 
sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM) 

def on_connect(mosq, obj, rc): 
     mqttc.subscribe(MQTT_Topic, 0) 

def on_message(mosq, obj, msg): 
     gps_handler(msg.topic, msg.payload) 

def gps_handler(Topic, jsonData): 
     jsonData = jsonData[1:-1] 
     sock.sendto(jsonData, (UDP_IP, UDP_RAW_PORT)) 
     print jsonData 

def on_subscribe(mosq, obj, mid, granted_qos): 
     pass 

mqttc = mqtt.Client() 

# Assign event callbacks 
mqttc.on_message = on_message 
mqttc.on_connect = on_connect 
mqttc.on_subscribe = on_subscribe 

# Connect 
mqttc.connect(MQTT_Broker, int(MQTT_Port), int(Keep_Alive_Interval)) 

# Continue the network loop 
mqttc.loop_forever()

当我执行

Traceback (most recent call last): 
    File "port_5567.py", line 38, in <module> 
    mqttc.loop_forever() 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 1470, in loop_forever 
    rc = self.loop(timeout, max_packets) 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 995, in loop 
    rc = self.loop_read(max_packets) 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 1273, in loop_read 
    rc = self._packet_read() 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 1838, in _packet_read 
    rc = self._packet_handle() 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 2291, in _packet_handle 
    return self._handle_connack() 
    File "/usr/local/lib/python2.7/dist-packages/paho/mqtt/client.py", line 2349, in _handle_connack 
    self.on_connect(self, self._userdata, flags_dict, result) 
TypeError: on_connect() takes exactly 3 arguments (4 given)

我不知道是什么原因让Ubuntu的服务器上的这个错误，

在树莓派（Debian的），它可以工作。

'mqttc.on_connect'是一个实例方法。它隐式地将实例作为第一个参数传递给方法（通常称为“self”） – Li357

谢谢！这很有用，但为什么在Raspberry Pi上不需要自己？ – Link

你在两台机器上使用哪种版本的Python（也是什么版本的Python MQTT库）？ – hardillb

答

尽管这些函数最初并未定义为类的一部分，但当您将它们称为类实例的方法时，Python将传递隐含的self参数，就像它们一直是您类的一部分一样。

要解决，只需添加self参数。

def on_connect(self, mosq, obj, rc): 
     self.subscribe(MQTT_Topic, 0) 

mqttc.on_connect = on_connect 

# Repeat for other functions as well.

谢谢！这很有用，但为什么在Raspberry Pi上不需要自己？ – Link

这与Raspberry Pi无关。这是一般python的行为。 – SethMMorton

类型错误：on_connect（）到底需要3个参数（4给出）

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