| Level | Exercise

Functions

Lets start with where we left off with variables.

def my_function(x):
  return x + 1

def findvolume(length=1, width=1, depth=1):
    print("Length = " + str(length))
    print("Width = " + str(width))
    print("Depth = " + str(depth))
    return length * width * depth

findvolume(1, 2, 3)
findvolume(length=5, depth=2, width=4)
findvolume(2, depth=3, width=4)

Some tasks need to be performed multiple times within a program.
Rather than rewrite the same code in multiple places, a function may be defined using the def keyword.
Function definitions may include parameters, providing data input to the function.
Functions may return a value using the return keyword followed by the value to return.

Calling a function: makeLight() wriing the function name followed by parentheses

Defining a function: def keyword followed by the name of the function, parentheses, and a colon

The body of the function, or the code for what the function will actually do, comes after the colon on an indented line

Function parameters:

Sometimes functions require input to provide data for their code. This input is defined using parameters.
Parameters are variables that are defined in the function definition.
They are assigned the values which were passed as arguments when the function was called, elsewhere in the code.

Function arguments:

Parameters in python are variables— placeholders for the actual values the function needs
When the function is called, these values are passed in as arguments.

import time

import board
import neopixel

pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=.1)

# Colors
BLACK = (0, 0, 0)
RED = (255, 0, 0)
PINK = (255, 100, 120)
ORANGE = (255, 100, 0)
YELLOW = (255, 255, 0)
GREEN = (0, 255, 0)
CYAN = (0, 255, 255)
PURPLE = (255, 0, 255)
BLUE = (0, 0, 255)
LIGHT_BLUE = (80, 200, 175)
WHITE = (255, 255, 255)

colors = [
    PINK,
    RED,
    ORANGE,
    YELLOW,
    GREEN,
    CYAN,
    PURPLE,
    BLUE,
    LIGHT_BLUE,
    WHITE
]

pixels.fill(BLACK)
pixels.show()

while True:
    for i in range(len(pixels)):
        pixels[i] = colors[i]
        time.sleep(.05)
    time.sleep(1)

And make a function out of the behavior:

def simpleCircle(wait):
    # Colors
    RED = (255, 0, 0)
    PINK = (255, 100, 120)
    ORANGE = (255, 100, 0)
    YELLOW = (255, 255, 0)
    GREEN = (0, 255, 0)
    CYAN = (0, 255, 255)
    PURPLE = (255, 0, 255)
    BLUE = (0, 0, 255)
    LIGHT_BLUE = (80, 200, 175)
    WHITE = (255, 255, 255)

    colors = [
        PINK,
        RED,
        ORANGE,
        YELLOW,
        GREEN,
        CYAN,
        PURPLE,
        BLUE,
        LIGHT_BLUE,
        WHITE
    ]

    for i in range(len(pixels)):
        pixels[i] = colors[i]
        time.sleep(.05)
    time.sleep(1)

How to use:

# CircuitPlaygroundExpress_NeoPixel
# https://learn.adafruit.com/adafruit-circuit-playground-express/circuitpython-neopixel

import time

import board
import neopixel

pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=.1)
pixels.fill((0, 0, 0))
pixels.show()

# choose which demos to play
# 1 means play, 0 means don't!
simpleCircleDemo = 1

def simpleCircle(wait):
    # Colors
    RED = (255, 0, 0)
    PINK = (255, 100, 120)
    ORANGE = (255, 100, 0)
    YELLOW = (255, 255, 0)
    GREEN = (0, 255, 0)
    CYAN = (0, 255, 255)
    PURPLE = (255, 0, 255)
    BLUE = (0, 0, 255)
    LIGHT_BLUE = (80, 200, 175)
    WHITE = (255, 255, 255)

    colors = [
        PINK,
        RED,
        ORANGE,
        YELLOW,
        GREEN,
        CYAN,
        PURPLE,
        BLUE,
        LIGHT_BLUE,
        WHITE
    ]

    for i in range(len(pixels)):
        pixels[i] = colors[i]
        time.sleep(wait)
    time.sleep(1)


while True:
    if simpleCircleDemo:
        print('Simple Circle Demo')
        simpleCircle(.05)
    pixels.fill((0, 0, 0))