如何將msg.payload全局用於MQTT Python客戶端？

Question

我想問一下，如果有使用msg.payload全球，而不只是在回調函數的方式。

貝婁是基本的回調函數：

# The callback for when a PUBLISH message is received from the server. 
def on_message(client, userdata, msg): 
    print(msg.topic+" "+str(msg.payload)) 
    # I usually then specify my steps here, but how can I use the variable outside? 


client = mqtt.Client() 
client.on_connect = on_connect 
client.on_message = on_message 

例如，我想要做這樣的事情：

def on_message(client, userdata, msg): 
    print(msg.topic+" "+str(msg.payload)) 
    return msg.payload 

global_data= on_message 
# do whatever I want with the data. I already tried to do this but it didn't work because 
# the client loops forever using client.loop_forever() 

Answer 1

使用，而不是client.loop功能client.start_loop功能。這將在一個單獨的線程上啓動網絡循環，允許您在主線程上執行自己的操作。

然後，您可以設置或從回調中改變一個全局變量的msg.payload的內容的價值。

E.g.

global_var 

def on_message(client, userdata, msg): 
    global global_var 
    print(msg.topic+" "+str(msg.payload)) 
    global_var = msg.payload