Abstraction 101

Making Python code more accessible

Transcript

1. Abstraction 101
   Making Python code more accessible
   Ben Nuttall
   Raspberry Pi Foundation
   

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2. Ben Nuttall
   ●
   Education Developer
   Advocate at the Raspberry Pi
   Foundation
   – Software & project
   development
   – Learning resources & teacher
   training
   – Community outreach
   ●
   @ben_nuttall on Twitter
   

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3. What is abstraction?
   ●
   Replacing commonly repeated blocks of code with generic
   implementations
   ●
   Simplifying commonly used software patterns
   ●
   Making domain specific interfaces from broad generic ones
   ●
   Only focusing on the details important to the user and their
   intentions
   

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4. Why use abstraction?
   ●
   Make programming more accessible
   ●
   Stop repeating code
   ●
   Simpler, more readable and understandable code
   ●
   Don't waste time reinventing the wheel (or googling how
   wheels work and copying it)
   ●
   Reduce friction and opportunities to give up (or not start)
   

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5. Abstraction is for lazy people?
   ●
   Yes and no
   – Yes, and it's good to be a lazy programmer! Learn to be faster and
   more efficient
   – No, it's for sensible people who just want to make progress
   

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6. Reduce the Learning Curve
   

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7. File Manager
   ●
   ls
   ●
   ls ­al
   ●
   cd
   ●
   pwd
   ●
   cp
   ●
   mv
   ●
   tree
   

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8. Turtle
   

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9. Pibrella
   ●
   Traffic Lights
   – red, amber, green
   ●
   Button
   ●
   Buzzer
   ●
   Labelled Inputs
   ●
   Labelled Outputs
   

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10. Pibrella
    pibrella.light.red.on()
    pibrella.light.amber.on()
    pibrella.light.green.on()
    pibrella.button.pressed(event)
    

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11. Flotilla
    

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12. Energenie
    #import the required modules
    import RPi.GPIO as GPIO
    import time
    # set the pins numbering mode
    GPIO.setmode(GPIO.BOARD)
    # Select the GPIO pins used for the encoder K0­K3 data inputs
    GPIO.setup(11, GPIO.OUT)
    GPIO.setup(15, GPIO.OUT)
    GPIO.setup(16, GPIO.OUT)
    GPIO.setup(13, GPIO.OUT)
    # Select the signal to select ASK/FSK
    GPIO.setup(18, GPIO.OUT)
    # Select the signal used to enable/disable the modulator
    GPIO.setup(22, GPIO.OUT)
    # Disable the modulator by setting CE pin lo
    GPIO.output (22, False)
    # Set the modulator to ASK for On Off Keying
    # by setting MODSEL pin lo
    GPIO.output (18, False)
    # Initialise K0­K3 inputs of the encoder to 0000
    GPIO.output (11, False)
    GPIO.output (15, False)
    GPIO.output (16, False)
    GPIO.output (13, False)
    # The On/Off code pairs correspond to the hand controller codes.
    # True = '1', False ='0'
    

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13. Energenie
    from energenie import switch_on, switch_off
    from time import sleep
    # turn all plug sockets on and off
    switch_on()
    switch_off()
    # turn a plug socket on and off by number
    switch_on(3)
    switch_off(3)
    

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14. PyGame Zero
    

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15. PyGame & PyGame Zero Sense HAT Apps
    

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16. RPi.GPIO and GPIO Zero
    import RPi.GPIO as GPIO
    from time import sleep
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    GPIO.setup(17, GPIO.OUT)
    while True:
    GPIO.output(17, GPIO.HIGH)
    sleep(1)
    GPIO.output(17, GPIO.LOW)
    sleep(1)
    from gpiozero import LED
    from time import sleep
    led = LED(17)
    while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)
    

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17. RPi.GPIO and GPIO Zero
    import RPi.GPIO as GPIO
    from time import sleep
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    GPIO.setup(17, GPIO.OUT)
    while True:
    GPIO.output(17, GPIO.HIGH)
    sleep(1)
    GPIO.output(17, GPIO.LOW)
    sleep(1)
    from gpiozero import LED
    led = LED(17)
    led.blink()
    

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18. GPIO Zero LED + Button
    from gpiozero import LED, Button
    led = LED(17)
    button = Button(3)
    button.when_pressed = led.on
    button.when_released = led.off
    

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19. GPIO Zero LED
    from gpiozero import LED
    led = LED(17)
    led.on()
    led.off()
    led.toggle()
    led.blink()
    

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20. RPi.GPIO Robot
    for pin in (14, 15, 17, 18):
    GPIO.setup(pin, GPIO.OUT)
    # forward
    GPIO.output(14, GPIO.LOW)
    GPIO.output(15, GPIO.HIGH)
    GPIO.output(17, GPIO.LOW)
    GPIO.output(18, GPIO.HIGH)
    

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21. GPIO Zero Robot
    from gpiozero import Robot
    robot = Robot(left=(14, 15), right=(17, 18))
    robot.forward()
    robot.left()
    robot.right()
    robot.stop()
    

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22. GPIO Zero Pre-defined Robots
    RyanteckRobot()
    CamJamKitRobot()
    

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23. An implementation of GPIO Zero (simplified)
    class LED():
    def __init__(self, pin):
    self.pin = pin
    GPIO.setup(pin, GPIO.OUT)
    def on(self):
    GPIO.output(self.pin, True)
    def off(self):
    GPIO.output(self.pin, False)
    >>> led = LED(17)
    >>> led.on()
    >>> led.off()
    

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24. GPIO Zero Traffic HAT Interface
    from gpiozero import TrafficHat
    hat = TrafficHat()
    hat.lights.green.on()
    hat.lights.amber.on()
    hat.lights.red.blink()
    hat.buzzer.beep()
    

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25. GPIO Zero Traffic HAT Interface
    hat.button.when_pressed = hat.on
    hat.button.when_released = hat.off
    hat.button.when_pressed = hat.lights.blink
    hat.button.when_released = hat.off
    hat.button.when_pressed = sequence
    

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26. Modules
    ●
    Standard library (e.g. time, datetime, signal, etc.)
    ●
    Third party modules (e.g. GPIO Zero, picamera, mcpi)
    – Some are pre-installed in Raspbian
    – Others you can download and install from pypi.python.org
    – apt­get install or pip install
    

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27. PyPI
    

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28. Import
    import picamera
    camera = picamera.PiCamera()
    

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29. Import
    from picamera import PiCamera
    camera = PiCamera()
    

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30. Import *
    from gpiozero import *
    button = Button(2)
    led = LED(3)
    

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31. Import from file
    from lesson_1 import forward, backward
    from time import sleep
    while True:
    forward()
    sleep(1)
    backward()
    sleep(1)
    

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32. Try it yourself!
    ●
    Maplin Robot Arm
    – MoveArm(1,[0,2,0])
    #Rotate base clockwise
    – MoveArm(1,[64,0,0])
    #Shoulder up
    ●
    Make your own traffic light
    set
    ●
    Make your own Pibrella /
    Traffic HAT
    

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33. Share your code!
    ●
    GitHub!
    ●
    Consider publishing as a module
    – See my talk “Building a Python API for Raspberry Pi Hardware”
    ●
    If a module already exists, consider contributing to it
    

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34. Abstraction 101
    Making Python code more accessible
    Ben Nuttall
    Raspberry Pi Foundation
    

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