wget \ http://archive.raspbian.org/raspbian/dists/stable/main/binary-armhf/Packages.xz \
-O - 2>/dev/null | xz -dfc | grep -c '^Package: ' \
| cut -d ' ' -f 2 

# Celsius to fahrenheit: F = ( C * 1.8 ) + 32
def celsius2fahrenheit( _celsius ):
  _fahrenheit = ( "%.2f" % (( _celsius * 1.8 ) + 32) )
  return float( _fahrenheit )

# Fahrenheit to celsius: C = ( F - 32 ) * 5/9
def fahrenheit2celsius( _fahrenheit ):
  _celsius = ( "%.2f" % (( _fahrenheit - 32 ) * 5/9 ))
  return float( _celsius )

#! /usr/bin/env bash
set -eu -o pipefail
DEBIAN_FRONTEND="noninteractive"
DEBIAN_PRIORITY="critical"
DEBCONF_NOWARNINGS="yes"
export DEBIAN_FRONTEND DEBIAN_PRIORITY DEBCONF_NOWARNINGS

_pkg_list="pigpio wiringpi python-rpi.gpio 
python3-rpi.gpio rpi.gpio-common git python-gpiozero 
python-gpiozero-doc python3-gpiozero python-setuptools-git python3-setuptools-git python3-dev python3-pip" 

# Upgrade system and installed packages - uncomment where 
# relevant
sudo apt update || ech o failed to update index list 
#sudo dpkg --configure -a || ech o failed to fix interrupted \
upgrades
#sudo apt --fix-broken --fix-missing install || ech o failed \
to fix conflicts 
#sudo apt -y --allow-downgrades --fix-broken --fix-missing \
#dist-upgrade

# Install $_pkg_list
sudo apt update
sudo apt-get -y install $_pkg_list

# Make 'pip3' bigly fresh? Yes.
sudo python3 -m pip --upgrade pip setuptools wheel
# Get Adafruit_DHT Python library
sudo pip3 install Adafruit_DHT

read -p "[?] Reboot? y/N: " _foo
if [ X"$_foo" = X"y" -o X"$_foo" = X"Y" ]
then 
  ech o "[!] Rebooting in 5 seconds, CTRL+C to abort ..."
  for i in $( seq 1 5 ) ; do ech o -n . ; sleep 1 ; done ; ech o
  sudo reboot
fi

bash rpi_prepare.sh

#! /usr/bin/env python3
# Demonstrate reading DHT22 sensor using the
# Adafruit_DHT library
# DHT22 pinout (left to right): 
# 1: VCC(3.3-6V) 
# 2: SIGNAL 
# 3: UNUSED 
# 4: GND
# Notes:
# - 10kOhm pull-up resistor from SIG to VCC.
# - Use 3V3 for VCC, or the DHT22 will heat up.
# - Indentation: 2 whitespaces per level, no tabs.
import Adafruit_DHT
from time import sleep
p=print # Alias 
# Note: Use >=2000ms polling intervals
_poll_interval = 2 # Seconds
_dht_pin = 24 # BCM24/BOARD18
_dht = Adafruit_DHT.DHT22

def celsius2fahrenheit( _celsius ):
  _fahrenheit = ( "%.1f" % (( _celsius * 1.8 ) + 32) )
  return float( _fahrenheit )

def fahrenheit2celsius( _fahrenheit ):
  _celsius = ( "%.1f" % (( _fahrenheit - 32 ) * 5/9 ))
  return float( _celsius )

if __name__ == '__main__':
  while True: 
    ( _humidity, _celsius ) = Adafruit_DHT.read_retry( _dht, _dht_pin )
    p( "Humidity => %.1f%% RH" % _humidity ) 
    p( "Temperature => %.2fF" % celsius2fahrenheit( _celsius ), end='/' )
    p( "%.2fC" % _celsius )
    sleep( _poll_interval )

python3 dht22_actionable.py

#! /usr/bin/env python3
# Install prerequisite packages & Adafruit_DHT library
"""
#! /bin/sh
_pkg_list='python3-setuptools python3-pip python3-dev python3-rpi.gpio'
sudo apt-get -y install $_pkg_list
sudo python3 -m pip --upgrade pip setuptools wheel
sudo pip3 install Adafruit_DHT
"""
#
# Ensure operating conditions in a 
# datacenter (your basement) are 
# within SAFE OPERATING HUMIDITY- AND 
# TEMPERATURE THRESHOLDS FOR OPTIMAL 
# COMPUTING CONDITIONS.
#
# Will fire BCM25/BOARD22 if humidity is 
# out of bounds, and BCM23/BOARD16 if 
# temperature is out of bounds. 
# 
# Uses RPi.GPIO Adafruit_DHT library, 
# tested on Raspbian, Dec. 2019
#
# DHT22 pinout (left to right):
# 1: VCC(3.3-6V)
# 2: SIGNAL
# 3: UNUSED
# 4: GND
# Notes:
# - 10kOhm pull-up resistor from SIG to VCC.
# - 330ohm resistors in series with RPi 
#   GPIO pins and ROHM SLR343BC4TT32
#   3mm LEDs.
# - Use 3V3 for VCC, or the DHT22 will 
#   heat up.
# - Indentation: 2 whitespaces per level, no 
#   tabs.
import Adafruit_DHT
from time import sleep
import RPi.GPIO as GPIO
import atexit
GPIO.setwarnings( True )
# Use BCM pin numbering instead of BOARD
GPIO.setmode( GPIO.BCM ) 
_humidity_led = 25 # BCM25/BOARD22
_humidity_lower_threshold = 45.0
_humidity_upper_threshold = 55.0
_temperature_led = 23 # BCM23/BOARD16
_temperature_lower_threshold = 20.0 # 20C/68F
_temperature_upper_threshold = 24.0 # 24C/75F
_poll_interval = 2 # Use intervals >=2secs
_dht_pin = 24 # BCM24/BOARD18
_dht = Adafruit_DHT.DHT22
_debug = True
p=print # Alias

if _debug:
  p( "[!] Setting up pin BCM_%i as OUTPUT for humidity LED ..." % _humidity_led )
  p( "[!] Setting up pin BCM_%i as OUTPUT for temperature LED ..." %  _temperature_led )

GPIO.setup( _humidity_led, GPIO.OUT )
GPIO.setup( _temperature_led, GPIO.OUT )

def exit_cleanly():
  print( "[!] Cleaning up and exiting ..." )
  GPIO.setwarnings( False )
  GPIO.cleanup()
  exit()

def celsius2fahrenheit( _celsius ):
  _fahrenheit = ( "%.1f" % (( _celsius * 1.8 ) + 32) )
  return float( _fahrenheit )

def fahrenheit2celsius( _fahrenheit ):
  _celsius = ( "%.1f" % (( _fahrenheit - 32 ) * 5/9 ))
  return float( _celsius )

# Call exit_cleanly on normal exit and CTRL+C/KeyboardInterrupt/foo
atexit.register( exit_cleanly )

if __name__ == '__main__':
  while True:
	( _humidity, _celsius ) = Adafruit_DHT.read_retry( _dht, 
        _dht_pin )
	if _debug:
  	p( "[+] Humidity => %.1f%% RH" % _humidity )
  	p( "[+] Temperature => %.1fC" % _celsius, end='/' )
  	p( "%.1fF" % celsius2fahrenheit( _celsius ) )
	# Let's be neat
	_humidity = float( "%.1f" % _humidity )
	_celsius = float( "%.1f" % _celsius )
	# Humidity too high?
	if _humidity > _humidity_upper_threshold:
  	p( 
        "[!] Humidity %.1f%% RH exceeds upper threshold value of %.1f%% RH" % 
        ( _humidity, _humidity_upper_threshold ) )
  	# Take decisive action!
  	GPIO.output( _humidity_led, 1 )
	# Humidity too low?
	elif _humidity < _humidity_lower_threshold:
  	p( 
        "[!] Humidity %.1f%% RH is below lower threshold value of %.1f%% RH" %  
         ( _humidity, _humidity_lower_threshold ) )
  	# Take decisive action!
  	GPIO.output( _humidity_led, 1 )
	# Safe operating humidity?
	elif _humidity <= _humidity_upper_threshold and _humidity >= _humidity_lower_threshold:
  	GPIO.output( _humidity_led, 0 )
  	# Safe!

	# Temperature too high?
	if _celsius > _temperature_upper_threshold:
  	p( "[!] Temperature %.1fC/%.1fF exceeds upper threshold value of %.1fC/%.1fF" %
  	( _celsius, celsius2fahrenheit( _celsius ), _temperature_upper_threshold,
  	celsius2fahrenheit( _temperature_upper_threshold ) ) )
  	# Take decisive action!
  	GPIO.output( _temperature_led, 1 )
	# Temperature too low?
	elif _celsius < _temperature_lower_threshold:
  	p( "[!] Temperature %1.fC/%.1fF is below lower threshold value of %.1fC/%.1fF" %
  	( _celsius, celsius2fahrenheit( _celsius ), _temperature_lower_threshold,
  	celsius2fahrenheit( _temperature_lower_threshold ) ) )
  	# Take decisive action!
  	GPIO.output( _temperature_led, 1 )
	# Safe operating temperature?
	elif _celsius <= _temperature_upper_threshold and _celsius >= _temperature_lower_threshold:
  	GPIO.output( _temperature_led, 0 )
  	# Safe!

	sl eep( _poll_interval )