Raspberry Pi Input Test 101

#!/usr/bin/python
''' rp_input_test101.py

the black terminal strip is located on the upper side of the Raspberry B+ board
there a two rows of 20 physical pins each
the upper row starts with the even pins 2 (upper left corner, ulc) to 40
the lower row starts with the odd pins 1 (lower left corner, llc) to 39

We will be using the following pins:
GND (pin 9)
GPIO_26 (pin 37)  RASP B+

You can tell the Raspberry Pi computer to set the input pin
normally low or high.

Pulldown setting (pin is kept low):
Connect a momentary pushbutton between +3.3V supply (pin 1) via a
1k ohm limiting resistor (for safety) to general purpose in/out GPIO_26
pressing the pushbutton will put 3.3 volt on GPIO_26 signaling an input

Pullup setting (pin is kept high):
Connect a momentary pushbutton between GND (pin 9) via a 1k ohm
limiting resistor (for safety) to general purpose in/out GPIO_26
pressing the pushbutton will put 0 volt on GPIO_26 signaling an input

To execute this code run IDLE as root (super user) via terminal command
sudo idle

or from the terminal (needs shebang line) ...
cd rpi_python
sudo python rp_input_test101.py

for parts used see ...
http://www.canakit.com/raspberry-pi-starter-ultimate-kit.html

code stored at

'''

import RPi.GPIO as gpio
import time

def input_26_sense(pulldown=True):
    # +3.3 volt applied to GPIO_26 gives True
    if gpio.input(26) and pulldown:
        return True
    # 0 volt applied to GPIO_26 gives True
    elif not gpio.input(26) and not pulldown:
        return True
    else:
        return False


# set board mode to Broadcom (recommended)
# gpio.BOARD would use the pysical pin numbers
gpio.setmode(gpio.BCM)

# this sets up a pulldown resistor internally
# input pin is kept low (around 0V)
gpio.setup(26, gpio.IN, pull_up_down=gpio.PUD_DOWN)
# this sets up a pullup resistor internally
# input pin is kept high (around +3.3V)
#gpio.setup(26, gpio.IN, pull_up_down=gpio.PUD_UP)


try:
    # wait till pushbutton has been pressed
    print("Press the pushbutton ...")
    while True:
        pulldown = True
        in26 = input_26_sense(pulldown)
        if in26 == True:
            print("Pushbutton pressed!")
            break
# respond to ctrl/c (in case electronics are not working)
except KeyboardInterrupt:
    # reset all GPIO to inactive
    gpio.cleanup()

#help(gpio)