Python script makes AssertionError when trying to MariaDB

Question

I have this piece of code that collects data from a HAT connected to a Raspberry. When run it gives this error:

[51.57, 22.30, 1002.01]
Traceback (most recent call last):
  File "dbWriter.py", line 45, in <module>
    write2DB(record)
  File "dbWriter.py", line 26, in write2DB
    assert len(values) == 3
AssertionError

I am by no means a programmer, i just fiddle around. It is meant to save 'record' to a database, which is then read and updated in realtime on an apache2 server. All help appreciated.

import mysql.connector
from itertools import repeat
import sys
import bme680
import time

try:
   sensor = bme680.BME680(bme680.I2C_ADDR_PRIMARY)
except IOError:
   sensor = bme680.BME680(bme680.I2C_ADDR_SECONDARY)

sensor.set_humidity_oversample(bme680.OS_2X)
sensor.set_pressure_oversample(bme680.OS_4X)
sensor.set_temperature_oversample(bme680.OS_8X)
sensor.set_filter(bme680.FILTER_SIZE_3)

mydb = mysql.connector.connect(
    host='localhost',
    user='pi',
    passwd='pass',
    database='weatherDB'
)
mycursor = mydb.cursor()

def write2DB(values):
    assert len(values) == 3
    sqlText = '''INSERT INTO data(humidity, temperature, pressure) VALUES({},{}, })'''.format(values[0], values[1], values[2])
    mycursor.execute(sqlText)
    mydb.commit()

for _ in repeat(None):
   sensor.get_sensor_data()
   output_humi = '{0:.2f}'.format(
       sensor.data.humidity)
   output_temp = '{0:.2f}'.format(
       sensor.data.temperature)
   output_pres = '{0:.2f}'.format(
       sensor.data.pressure)
   record = []
   record = ('[' + (output_humi) + ', ' + (output_temp) + ', ' + (output_pres) + ']')
   print(record)
   write2DB(record)
   time.sleep(10)
   pass

Booboo · Accepted Answer · 2020-07-06 15:05:52Z

1

You have:

record = ('[' + (output_humi) + ', ' + (output_temp) + ', ' + (output_pres) + ']')

record evaluates to a single string, not a list of 3 elements and hence your exception.

Change the above to:

record = [output_humi, output_temp, output_pres]

You are also missing a { in your format specification. It should be:

sqlText = '''INSERT INTO data(humidity, temperature, pressure) VALUES({},{}, {})'''.format(values[0], values[1], values[2])

An alternative would be to use a prepared statement:

sqlText = 'INSERT INTO data(humidity, temperature, pressure) VALUES(%s, %s, %s)'
mycursor.execute(sqlText, values)

In the above case you will be passing actual strings as the values. I don't know how the columns are defined, but no matter. If they are defined as floating point or decimal values, the strings will be converted to the correct type.

edited Jul 6, 2020 at 15:05

answered Jul 6, 2020 at 14:48

Booboo

45.7k4 gold badges46 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python script makes AssertionError when trying to MariaDB

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related