title: How to update rrd database in python
body: <p>I am new to the programing and I am using already created scripts, I am trying to update my RRD database in python. I have manage to create below code which don’t come back to me with any errors but when I am trying to generate a graph it don’t contain any data.</p>
  
  <pre><code>#!/usr/bin/python
  
  #modules
  import sys
  
  import os
  
  import time
  
  import rrdtool
  
  import Adafruit_DHT as dht
  
  #assign data
  h,t = dht.read_retry(dht.DHT22, 22)
  
  #display data
  print 'Temp={0:0.1f}*C'.format(t, h)
  print 'Humidity={1:0.1f}%'.format(t,h)
  
  #update database
  data = "N:h:t"
  ret = rrdtool.update("%s/humidity.rrd" % (os.path.dirname(os.path.abspath(__file__))),data)
  
  if ret:
   print rrdtool.error()
   time.sleep(300)
  </code></pre>
  
  <p>Below my data base specification:</p>
  
  <pre><code>#! /bin/bash
  rrdtool create humidity.rrd \
  --start "01/01/2015" \
  --step 300 \
   DS:th_dht22:GAUGE:1200:-40:100 \
   DS:hm_dht22:GAUGE:1200:-40:100 \
   RRA:AVERAGE:0.5:1:288 \
   RRA:AVERAGE:0.5:6:336 \
   RRA:AVERAGE:0.5:24:372 \
   RRA:AVERAGE:0.5:144:732 \
   RRA:MIN:0.5:1:288 \
   RRA:MIN:0.5:6:336 \
   RRA:MIN:0.5:24:372 \
   RRA:MIN:0.5:144:732 \
   RRA:MAX:0.5:1:288 \
   RRA:MAX:0.5:6:336 \
   RRA:MAX:0.5:24:372 \
   RRA:MAX:0.5:144:732 \
  </code></pre>