Set maximum and minimum value of temperature and humidity that will be inserted to MySQL using Python

I have some questions about how can we set a max/min value of temperature or humidity because sometimes during restart, the value of humidity suddenly spiked to >5000% or sometimes the temperature >100C.

So, I want to make sure that this data is not inserted to the SQL and filtered using python script added to the .py

Should I change this line?

            if temp is not and hum is not None:

import serial
import time
import pymysql.cursors
#Connect to database
connection = pymysql.connect(host='localhost',
                             user='ubuntu',
                             password='testing',
                             database='Blabla',
                             cursorclass=pymysql.cursors.DictCursor)
arduino = serial.Serial('/dev/ttyACM0', 9600)
print('Established serial connection to Arduino')
with connection:
    while True:
            arduino_data = arduino.readline()
            decoded_values = str(arduino_data[0:len(arduino_data)].decode("utf-8"))
            list_values = decoded_values.split(' ')
            print(f'Collected readings from Arduino: {list_values}')
            arduino_data = 0
            temp = list_values[0]
            hum = list_values[1]
            #Here we are going to insert the data into the Database
            if temp is not and hum is not None:
                with connection.cursor() as cursor:
                    cursor.execute("INSERT INTO `SensorTest` (`Temperature`, `Humidity`) VALUES (%s,%s)", (temp,hum))
                    connection.commit()
                    cursor.close()
            else:
                print('Failed to read the sensor')
            time.sleep(60)

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Solution

Sure you can add more filters to this line to make sure the values are not wrong.

I would recommended setting const valid minimum and maximum values for both temp and hum at the start of the script (after the imports), for example:

MIN_VALID_TEMP = -20
MAX_VALID_TEMP = 90
MIN_VALID_HUM = 10
MAX_VALID_HUM = 1000

Next I would recommend splitting the temp and hum validation to an helper functions, such as:

def validate_reading(temp, hum):
    if not temp or not hum:
        return false
    if (temp > MIN_VALID_TEMP  and temp < MAX_VALID_TEMP and
    hum > MIN_VALID_HUM and hum < MAX_VALID_HUM):
        return true
    return false

and switch your original if:

if temp and hum is not None:

to:

if validate_reading(temp, hum):

Also what you can do next is to add a different print when the reading is not valid!

The final file will look like this:

import serial
import time
import pymysql.cursors

# define valid temp and hum
MIN_VALID_TEMP = -20
MAX_VALID_TEMP = 90
MIN_VALID_HUM = 10
MAX_VALID_HUM = 1000


def validate_reading(temp, hum):
    if not temp or not hum:
        return False
    if temp > MIN_VALID_TEMP and temp < MAX_VALID_TEMP and hum > MIN_VALID_HUM and hum < MAX_VALID_HUM:
        return True
    return False


# Connect to database
connection = pymysql.connect(
    host="localhost", user="ubuntu", password="testing", database="Blabla", cursorclass=pymysql.cursors.DictCursor
)
arduino = serial.Serial("/dev/ttyACM0", 9600)
print("Established serial connection to Arduino")
with connection:
    while True:
        arduino_data = arduino.readline()
        decoded_values = str(arduino_data[0 : len(arduino_data)].decode("utf-8"))
        list_values = decoded_values.split(" ")
        print(f"Collected readings from Arduino: {list_values}")
        arduino_data = 0
        temp = list_values[0]
        hum = list_values[1]
        # Here we are going to insert the data into the Database
        if validate_reading(temp, hum):
            with connection.cursor() as cursor:
                cursor.execute("INSERT INTO `SensorTest` (`Temperature`, `Humidity`) VALUES (%s,%s)", (temp, hum))
                connection.commit()
                cursor.close()
        else:
            print("Failed to read the sensor")
        time.sleep(60)