Read and subscribe to BLE sensors from Python with Bleak

Bleak is an async, cross-platform BLE client: BlueZ on Linux, Core Bluetooth on macOS, WinRT on Windows.

pip install bleak

import asyncio

from bleak import BleakClient, BleakScanner
from bleak.backends.characteristic import BleakGATTCharacteristic

DEVICE_NAME = "MySensor"
BATTERY_LEVEL = "00002a19-0000-1000-8000-00805f9b34fb"   # standard Battery Level
DATA_CHAR = "your-128-bit-characteristic-uuid"             # your notify characteristic


def on_data(sender: BleakGATTCharacteristic, data: bytearray) -> None:
    print(f"{sender.uuid}: {data.hex()}")


async def main() -> None:
    device = await BleakScanner.find_device_by_name(DEVICE_NAME, timeout=10.0)
    if device is None:
        raise SystemExit(f"{DEVICE_NAME} not found")

    async with BleakClient(device) as client:          # connects, disconnects on exit
        battery = await client.read_gatt_char(BATTERY_LEVEL)
        print("battery:", battery[0], "%")

        await client.start_notify(DATA_CHAR, on_data)  # writes the CCCD for you
        await asyncio.sleep(60)                         # receive notifications
        await client.stop_notify(DATA_CHAR)


asyncio.run(main())

Notes from practice

• Pass the BLEDevice from the scanner to BleakClient rather than an address string where possible; on some backends this avoids an extra scan.
• Linux/BlueZ: the user needs access to the system D-Bus Bluetooth service (typically the bluetooth group or running as a service with the right policy). Keep BlueZ reasonably current; Bleak documents the minimum supported version.
• macOS uses Core Bluetooth UUIDs instead of MAC addresses as device addresses (see the iOS identity warning).
• Reconnects: wrap the async with block in a retry loop with backoff; sensors drop links.
• One adapter, many devices: keep the number of simultaneous connections modest and test your adapter's limit; scanning while connected reduces throughput on many controllers.
• Decode payloads explicitly (int.from_bytes(data[0:2], "little", signed=True)) instead of assuming structure.