Python 虚拟设备句柄更改事件来自 azure IoT 集线器

Question

So, I'm fairly new to python and have run into an issue which I really can't wrap my head around.

I have a virtual device that I have programmed in python that connects to Azure IoT hub. As some of you probably know, devices that are connected to IoT hub have a device twin, which defines the properties of the device. (It's a basic JSON object)

The idea with this is, that the backend can change the device twin, which on the device may have an effect on the mode of operation.

Thus far, I just want to achieve the following, which is very basic:

1. My virtual device listens for device twin changes (Without locking my code)
2. I change a device twin property in Azure
3. The event fires and prints out the new device twin properties (Eventully, this should call some other code, to change the mode of operation)

So far I have the following:

async def main():
   
    async def printdesiredproperties():
        while True:
            test = await my_client.receive_twin_desired_properties_patch() #This returns a JSON dict
            print(test)
    
    task = asyncio.create_task(printdevicetwin()) #not correct way to attach event
    await task
    #Do other stuff

From my experience in other programming languages, we are used to attaching and detaching eventhandlers with respectively += and -=.

In python there seems to be a lot of ways to achieve this, however I really haven't had success with any of them.

my_client.receive_twin_desired_properties_patch() is what raise an event, in the sense that it returns a JSON dict when a change is made in Azure

Answer 1

Try the code below:

import time
import threading

from azure.iot.device import IoTHubDeviceClient
from azure.iot.device.iothub.sync_clients import IoTHubModuleClient

CONNECTION_STRING = "<device conn str>"

def iothub_client_init():
    
    client = IoTHubDeviceClient.create_from_connection_string(CONNECTION_STRING)
    
    return client

def twin_update_listener(client):
    while True:
        patch = client.receive_twin_desired_properties_patch()
        print("Twin patch received:")
        print(patch)
       

def iothub_client_init():
    client = IoTHubModuleClient.create_from_connection_string(CONNECTION_STRING)
    return client

def iothub_client_sample_run():
    try:
        client = iothub_client_init()

        twin_update_listener_thread = threading.Thread(target=twin_update_listener, args=(client,))
        twin_update_listener_thread.daemon = True
        twin_update_listener_thread.start()
        count = 0;
        while True:
            count += 1
            print ( "Sending data as reported property..." )
            reported_patch = {"ReportCount": count}
            client.patch_twin_reported_properties(reported_patch)
            print ( "Reported properties updated:" + str(count))
            time.sleep(5)
    except KeyboardInterrupt:
        print ( "IoT Hub Device Twin device sample stopped" )

if __name__ == '__main__':
    print ( "Starting the Python IoT Hub Device Twin device sample..." )
    print ( "IoTHubModuleClient waiting for commands, press Ctrl-C to exit" )

    iothub_client_sample_run()

While I change some value in desired of twin:

Counting is continuing and we also get the event: