python mqtt subscribe

要在Python中使用MQTT订阅消息，你可以使用paho-mqtt库。首先，你需要安装paho-mqtt库。然后，你可以使用以下代码来订阅消息：

from paho.mqtt import client as mqtt
import uuid

def on_connect(client, userdata, flags, rc):
    """一旦连接成功, 回调此方法"""
    rc_status = \["连接成功", "协议版本不正确", "客户端标识符无效", "服务器不可用", "用户名或密码不正确", "未经授权"\]
    print("connect：", rc_status\[rc\])

def on_message(client, userdata, msg):
    """一旦订阅到消息, 回调此方法"""
    print("主题:"+msg.topic+" 消息:"+str(msg.payload.decode('gb2312')))

def mqtt_connect():
    """连接MQTT服务器"""
    mqttClient = mqtt.Client(str(uuid.uuid4()))
    mqttClient.on_connect = on_connect  # 返回连接状态的回调函数
    mqttClient.on_message = on_message  # 返回订阅消息回调函数
    MQTTHOST = "IP"  # MQTT服务器地址
    MQTTPORT = 1883  # MQTT端口
    mqttClient.username_pw_set("username", "password")  # mqtt服务器账号密码
    mqttClient.connect(MQTTHOST, MQTTPORT, 60)
    mqttClient.loop_start()  # 启用线程连接
    return mqttClient

def on_subscribe():
    """订阅主题：mqtt/demo"""
    mqttClient = mqtt_connect()
    mqttClient.subscribe("mqtt/demo", 2)
    while True:
        pass

if __name__ == '__main__':
    on_subscribe()

这段代码使用paho-mqtt库创建了一个MQTT客户端，并连接到MQTT代理。然后，它订阅了主题"mqtt/demo"，并在收到消息时调用了on_message函数进行处理。你可以根据需要修改主题和其他参数。
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