This script periodically polls the DHT11 sensor for Temperature and humidity data, logs it locally to a csv file and also sends the data to ThingSpeak.

getTempHumData.py

"""
Humidity and Temperature data logging script.
For ANLY 510 class
Anurag Kotha

Based on below sketch.
Temperature/Humidity Light monitor using Raspberry Pi, DHT11, and photosensor 
Data is displayed at thingspeak.com
2015/06/15
SolderingSunday.com

Based on project by Mahesh Venkitachalam at electronut.in

"""


# Import all the libraries we need to run
import sys
import os
import time
import Adafruit_DHT
import urllib2



pwd = "/home/pi/TempHum/"
DEBUG = 0
# Setup the pins we are connected to
DHTpin = 4

#Setup our API and delay
myAPI = "TEMP Value" # *** SET YOUR API KEY HERE. WONT WORK OTHERWISE
myDelay = 45 #how many seconds between posting data

# File name for data logging
fname = pwd + 'TemHumLog_'+time.strftime("%d%m%Y", time.gmtime()) + '.csv'
# File name for error recovery
fErrRec = pwd + 'TempHumErrorStatus.log'

def getSensorData():
    RHW, TW = Adafruit_DHT.read_retry(Adafruit_DHT.DHT11, DHTpin)
    #Convert from Celius to Farenheit
    TWF = 9/5*TW+32
    # return dict
    return (str(RHW), str(TW),str(TWF))

# main() function
def main():
    
    print 'starting... '

    baseURL = 'https://api.thingspeak.com/update?api_key=%s' % myAPI
    print baseURL

    while True:
	
		try:
			mTime = time.strftime("%d/%m/%Y %H:%M:%S",time.gmtime())
			RHW, TW, TWF = getSensorData()

			# Log data to file
        		mData = "%s,%s,%s,%s\n" %(mTime,TW,TWF,RHW)
            		logfile = open(fname,'a',0)
            		logfile.write(mData)
	            	logfile.close()
          
	    		# Log error status to file
            		logfile = open(fErrRec,'a',0)
            		logfile.write("1\n")
            		logfile.close()
			time.sleep(int(myDelay))

        	except:
            		# Log error status to file
            		logfile = open(fErrRec,'a',0)
            		logfile.write("0\n")
            		logfile.close()
            		print 'Exception caught'
            		# break  		  Dont want to exit everytime we loose network connection.

		try:
        		# Send data to ThingSpeak takes some time to open the connection
        		f = urllib2.urlopen(baseURL +                               "&field1=%s&field2=%s&field3=%s" % (TW, TWF, RHW)+ "&field4=%s" % ("1"))
       			print f.read()
    			print TW + " " + TWF+ " " + RHW + " " + "1"
			f.close()
		except:
			
			# Log error status to file
            		logfile = open(fErrRec,'a',0)
        		logfile.write("0")
       	    		logfile.close()
       			print 'Failed to connect to the server.'

            
			
# call main
if __name__ == '__main__':
    main()