sensors.py

#!/usr/bin/python
from __future__ import print_function
import boto3
import time
import datetime
import sys
import Adafruit_DHT
from decimal import Decimal 

# Type of sensor, can be Adafruit_DHT.DHT11, Adafruit_DHT.DHT22, or Adafruit_DHT.AM2302.
DHT_TYPE = Adafruit_DHT.AM2302 #quals to just 22

# GPIO data pins connected to Raspberry Pi pin in an array
DHT_PINS_ARRAY = [2,3,4]

#Sensors IDs
SENSORS_IDS = ['sensorA', 'sensorB', 'sensorC']

#Variables
temperatureA = temperatureB = temperatureC = 0
humidityA = humidityB = humidityC = 0

# Get the service resource.
dynamodb = boto3.resource('dynamodb')

# Instantiate a table resource object without actually
# creating a DynamoDB table using an already creaded one.
table = dynamodb.Table('ladfyu-sensors')

# index
i = 0

    
while True:
	
	humidity, temperature = Adafruit_DHT.read(22, DHT_PINS_ARRAY[i]) #Attempt a reading
	
	if humidity is not None and temperature is not None: 
		
		humidity = Decimal(temperature).quantize(Decimal('0.01'))
		temperature = Decimal(temperature * 1.8 + 32).quantize(Decimal('0.01')) #converted to 2 decimal points and farenth
		current_time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")	# datetime.datetime to string
		
		with open('output.csv', 'a') as f: #Keep a local copy in output.csv of the data
			print(current_time, SENSORS_IDS[i], temperature, humidity, sep=',', file=f)	
	
		try:	
			#Send data to table
			table.put_item(
				Item={	'reading_id': current_time,
						'sensor_id': SENSORS_IDS[i],
						'humidity': humidity,
						'temperature': temperature
				}
			)
			print ("logged")		
        
		except:
			# Error appending data, most likely because of a network error
			print('Append error, check network connection')
			time.sleep(30)
			continue  
        
        
	else:
		time.sleep(5)
		print ('temp or hum is None')
		continue
	
	  	
	print(SENSORS_IDS[i], DHT_PINS_ARRAY[i], temperature, humidity)  
	time.sleep(5)
	if i == 2: i = -1 				#restart index for pins and sensors array
	i = i + 1
    
    


#Tutorial followed http://boto3.readthedocs.io/en/latest/guide/dynamodb.html?highlight=dynamo