Python code for reading DHT20 sensor from Raspberry Pi (improved)

dht20_v2.py

#!/usr/bin/python3

# Import stuff
import smbus
from time import sleep
from os import remove


class Lock:
    # Constructor - define class-wide variables
    def __init__(self, path):
        self.path = path
        self.fd = None # File descriptor

    # Locking function - attempt to create lockfile, return success
    def lock(self):
        try:
            self.fd = open(self.path, "x")
        except FileExistsError:
            return False
        else: # If no exception is raised
            return True

    # Unlocking function - delete lockfile, call destructor
    def unlock(self):
        self.__del__()
        remove("/var/lock/dht20")

    # Destructor - close lockfile, change file descriptor to null
    def __del__(self):
        if self.fd != None:
            self.fd.close()
            self.fd = None


class DHT20:
    def __init__(self):
        # Initialize lock
        self.lock = Lock("/var/lock/dht20")

        # Open I2C bus, handle permission error
        try:
            self.bus = smbus.SMBus(1) # We assume you are connected to the first I2C bus
        except PermissionError:
            print("Could not open I2C bus: Permission denied.")
            print("Try re-running the script as root.")
            exit(1)

    def read(self):
        # Acquire lock on device
        if self.lock.lock() == False:
            print("Could not acquire lock. The device is currently in use.")
            print("Please try again later.")
            exit(1)

        # Get raw data from device, close I2C bus
        self.bus.write_i2c_block_data(0x38, 0xAC, [0x33, 0x00]) # I2C address, start register, data - list of bytes
        sleep(0.1) # Give it some time to measure
        raw_data = self.bus.read_i2c_block_data(0x38, 1, 7) # I2C address, start register, block length

        # Release lock, close I2C bus
        self.lock.unlock()
        self.bus.close()

        return self.calculate(raw_data)

    def calculate(self, raw_data):
        # Perform some fancy calculations I copied from the Internet :)
        temp = 0
        temp = (temp | raw_data[3]) << 8
        temp = (temp | raw_data[4]) << 8
        temp = temp | raw_data[5]
        temp = temp & 0xfffff
        temp = (temp * 200 * 10 / 1024 / 1024 - 500)/10

        humidity = 0
        humidity = (humidity | raw_data[1]) << 8
        humidity = (humidity | raw_data[2]) << 8
        humidity = humidity | raw_data[3]
        humidity = humidity >> 4
        humidity = (humidity * 100 * 10 / 1024 / 1024)/10

        return temp, humidity


# Print output if the program is not imported itself
if __name__ == "__main__":
    # Initialize sensor, do measurement
    sensor = DHT20()
    temp, humidity = sensor.read()

    # Print result rounded to 3 decimals
    print(f"Temperature: {round(temp, 3)} °C")
    print(f"Humidity: {round(humidity, 3)} % RH")
    exit(0)