Part of the DHT11 python driver based on http://www.uugear.com/portfolio/dht11-humidity-temperature-sensor-module/# It has problem with proper response time, and few others, better use adafruit driver

SensorDHT11.py

import RPi.GPIO as GPIO
import time
from datetime import datetime

def bin2dec(string_num): # define a function to convert a binary number to a decimal.
    return str(int(string_num, 2)) # return the string representing the integer value of the string passed to this function in base 2 (binary)


class Sensor(object):
	def __init__(self):
		self._reset_data()
		

	def _reset_data(self):
		self.data = []
		self.total_bits = 0
		self.count = 0
		self.humidity_bit = ""
		self.temperature_bit = ""
		self.crc = ""


	def _initiate_sensor_readout(self):
		GPIO.setmode(GPIO.BCM) # use the Broadcom numbers instead of the WiringPi numbers
		GPIO.setup(4,GPIO.OUT)  # Set it as an output so that we can:
		GPIO.output(4,GPIO.HIGH) # write a 1
		time.sleep(0.025) # for 25 ms
		GPIO.output(4,GPIO.LOW) # then write a 0
		time.sleep(0.02) # for 20 ms.
		GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Change the pin to read mode, with a pullup resistor

	def _check_crc(self):
		try:
			for i in range(0, 8): # do this 9 times
			      self.total_bits = 0 # reset the bit self.counter

			      while self.data[self.count] == 0: # as long as a 0 was read
			         self.count = self.count + 1 # move on to the next bit

			      while self.data[self.count] == 1: # as long as a 1 was read
			         self.total_bits = self.total_bits + 1 # self.count how many 1s
			         self.count = self.count + 1 # move on to the next bit

			      if self.total_bits > 3: # if there were at least 3 * 1-bits
			         self.crc = self.crc + "1" # add a 1 to the self.crc (Cyclic redundancy check) bitstring
			      else: # if there were less than 3* 1-bits
			         self.crc = self.crc + "0" # add a 0 to the self.crc bitstring
		except IndexError:
			raise BitDataRangeError
		else:
			self.Humidity = bin2dec(self.humidity_bit) # convert the binary bitstring to a decimal variable for humidity
			self.Temperature = bin2dec(self.temperature_bit)
			if int(self.Humidity) + int(self.Temperature) - int(bin2dec(self.crc)) != 0:
				raise BitDataCrcError
	

	def _pull_data(self):
		for i in range(0,500): # 501 times
			self.data.append(GPIO.input(4)) # read a bit from the GPIO, as fast as possible (no wait)

		#with open('dump.txt','w') as f:
		#	f.write(str(self.data)) 36 22

	def _process_readout(self):
		try:
			while self.data[self.count] == 1: # as long as you read a 1
				self.count = self.count + 1 # self.count how many 1s have been read
			for i in range(0, 32): # do this 33 times
				self.total_bits = 0 # reset the bit self.count each time

				while self.data[self.count] == 0: # as long as a 0 is read
					self.count = self.count + 1 # move on to the next bit

				# opnening [1, 0, 0, 0, 0, (1,) 0, 0, 0, 0...
				while self.data[self.count] == 1: # as long as a 1 is read
					self.total_bits = self.total_bits + 1 # self.count how many 1s in a row
					self.count = self.count + 1 # move on to the next bit

				if self.total_bits > 3: # if there were mote than 3 * 1-bits in a row
					if i>=0 and i<8: # if we're in the first byte
						self.humidity_bit = self.humidity_bit + "1" # append a 1 to the humidity bitstring
					if i>=16 and i<24: # if we're in the 3rd byte
						self.temperature_bit = self.temperature_bit + "1" # add a 1 to the temperature bitstring
				else: # if there weren't at least 3 * 1-bits
					if i>=0 and i<8: # if we're in the first byte
						self.humidity_bit = self.humidity_bit + "0" # append a 0 to the humidity bitstring
					if i>=16 and i<24: # if we're in the 3rd byte
						self.temperature_bit = self.temperature_bit + "0" # append a 0 to the temperature bitstring
		except IndexError:
			raise BitDataRangeError

	def read(self):
		self._reset_data
		self._initiate_sensor_readout()
		try:
			self._pull_data()
			self._process_readout()
			self._check_crc()
		except (BitDataCrcError, BitDataRangeError):
			self.Humidity = None
			self.Temperature = None
		self.readout_time = datetime.now()
		return self.Humidity, self.Temperature, self.readout_time

		


class BitDataRangeError(Exception):
	pass


class BitDataCrcError(Exception):
	pass
 # convert the binary bitstring to a decimal variable for temperature