全局变量未随Python和MQTT更改

Question

我正在尝试运行一个MQTT客户端，该客户端同时接收和发布消息。我正在尝试做的是在收到消息时停止while循环，该循环负责发布。但是，对于while循环，运行永远不会为False，并且循环永远不会中断。我该怎么办？我只想在收到消息时打破循环。这是我的代码：

running = True
def on_message(client, userdata, msg):
     print(msg)
     running = False
     print(running) # it becomes False here

client.on_connect = on_connect
client.on_message = on_message
client.connect(HOST, 1883, 60)

client.loop_start() # used to receive on_message events while the while loop is true 

while running:
    #publish and do something until running is False