Can't import python Async functions, throws 'Python Error: RuntimeError: Cannot change thread mode after it is set'

So, I have created a python API which uses Bleak and Winrt library to connect to a BLE device and write to a specific characteristic.

Now, usually I try to import the API using py.importlib.import_module() and then do a py.importlib.reload().

But now when I do this I get the error - Python Error: RuntimeError: Cannot change thread mode after it is set.This error is encountered due to winrt library. If I comment that out I won't get any error when I press run.

But now the next error I encounter is after running the API functions. Which states : sys:1: RuntimeWarning: coroutine 'getBleDetails' was never awaited. RuntimeWarning: Enable tracemalloc to get the object allocation traceback

The Codes are attached below :

test_ble.m

% Set the threading mode in Python before importing the module
pe = eval("pyenv");
if ~strcmp(pe.Version,'3.9')
    eval("pyenv('Version','3.9')");
end

% Import the Python module and reload it
try
    bluetooth_ble = py.importlib.import_module('bluetooth_handler');
    py.importlib.reload(bluetooth_ble);
catch ME
    disp(ME)
end
fname = 'bluetoothAddr.txt';
script_file = fileread(fname);
line = split(script_file,newline);
bluetoothMac = strip(line{1});

response = eval("py.bluetooth_handler.getBleDetails(bluetoothMac)");

response = eval("bluetooth_ble.sendCommand(bluetoothMac)")

bluetooth_handler.py

import asyncio
from bleak import BleakScanner, BleakClient
from winrt.windows.devices import radios
import struct


async def powerBluetooth(state):
    """
    Method to Turn On, Off system Bluetooth

    Args:
        state (str): Enter `ON` to turn on device Bluetooth or `OFF` to turn off device Bluetooth

    Returns:
        bool: Returns `True` is successfully set Bluetooth or `False` on failure 
    """
    
    try:
        all_radios = await radios.Radio.get_radios_async()
        bluetooth_radio = None

        for this_radio in all_radios:
            if this_radio.kind == radios.RadioKind.BLUETOOTH:
                bluetooth_radio = this_radio
                break

        if bluetooth_radio is not None:
            if state == "ON":
                if bluetooth_radio.state != radios.RadioState.ON:
                    await bluetooth_radio.set_state_async(radios.RadioState.ON)
            else:
                if bluetooth_radio.state != radios.RadioState.OFF:
                    await bluetooth_radio.set_state_async(radios.RadioState.OFF)
        else:
            print("Bluetooth Radio not found.")

        return True  # Success

    except Exception as e:
        print(f"An error occurred while powering Bluetooth: {str(e)}")
        return False  # Failure



async def sendCommand(address,mode='normalmode'):
    try:
        async with BleakClient(address) as client:
            # print('Got Connection')
            # await asyncio.sleep(10)
            
            config_uuid = 'xxx-xxx-xxx'
            config_char = client.services.get_characteristic(config_uuid)

            if config_char:
                try:
                    
                    // Read write characteristics

                except Exception as e:
                    print(f'Error Setting Mode : {e}')
                    return False
            else:
                print('Requested Characteristic not found')
                return False
            
    except Exception as e:
        print(f'Error Connecting Device : {e}')
        return False

if __name__ == "__main__":
    # asyncio.run(bleDiscover())
    devAddr = asyncio.run(getBleDetails())
    if devAddr:
        asyncio.run(sendCommand(devAddr))
    else:
        print("Device not found")

My reason to use Python and not MATLAB in-built BLE function is : MATLAB BLE interface requires the device to be manually paired to the PC. While using python code I can choose which device to pair.

How can I import this API to work with MATLAB ?

[Malay Agarwal]

Hi @palak,

Your Python code seems to be missing the getBleDetails function. Could you post the code for the function?