You do not need to remove power to restart Pi. There are a pair of pads near the SD Card (I think labelled reset possibly run - I can't see on my Pi because they all have switch soldered on the board.) Momentarily short to restart.
Recent Rasbpian have an in-built process for shutdown (handled by systemd-logind)
Add the following to /boot/config.txt
dtoverlay=gpio-shutdown,gpio_pin=5
This enables a switch connected between pin 29 (GPIO 5) and pin 30 (Gnd) to initiate an orderly shutdown of the Pi.
Almost any pin can be used - the default is pin 5 (GPIO 3), although this is often used for I²C
,gpio_pin=21 would use the same pins used in the script pin 40 (GPIO 21) and pin 39 (Gnd)
I recommend sudo poweroff to shut down the Pi. There is nothing wrong with what you are doing, but poweroff causes the green LED to blink 10 times at 1 second intervals when it is safe to poweroff.
Just to be clear - the following script was the original Answer. While it should work it is no longer necessary.
I have a Python script which shuts the Pi down with a pushbutton.
#!/usr/bin/env python2.7
#-------------------------------------------------------------------------------
# Name: Shutdown Daemon
#
# Purpose: This program gets activated at the end of the boot process by
# cron. (@ reboot sudo python /home/pi/shutdown_daemon.py)
# It monitors a button press. If the user presses the button, we
# Halt the Pi, by executing the poweroff command.
#
# The power to the Pi will then be cut when the Pi has reached the
# poweroff state (Halt).
# To activate a gpio pin with the poweroff state, the
# /boot/config.txt file needs to have :
# dtoverlay=gpio-poweroff,gpiopin=27
#
# Author: Paul Versteeg
#
# Created: 15-06-2015, revised on 18-12-2015
# Copyright: (c) Paul 2015
# https://www.raspberrypi.org/forums/viewtopic.php?p=864409#p864409
#-------------------------------------------------------------------------------
import RPi.GPIO as GPIO
import subprocess
import time
GPIO.setmode(GPIO.BCM) # use GPIO numbering
GPIO.setwarnings(False)
# I use the following two GPIO pins because they are next to each other,
# and I can use a two pin header to connect the switch logic to the Pi.
# INT = 17 # GPIO-17 button interrupt to shutdown procedure
# KILL = 27 # GPIO-27 /KILL : this pin is programmed in /boot/config.txt and cannot be used by any other program
INT = 21 # GPIO button interrupt to shutdown procedure
# use a weak pull_up to create a high
GPIO.setup(INT, GPIO.IN, pull_up_down=GPIO.PUD_UP)
def main():
while True:
# set an interrupt on a falling edge and wait for it to happen
GPIO.wait_for_edge(INT, GPIO.FALLING)
# print "button pressed"
time.sleep(1) # Wait 1 second to check for spurious input
if( GPIO.input(INT) == 0 ) :
subprocess.call(['poweroff'], shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
if __name__ == '__main__':
main()
