Python - Higher Order Functions, Instances and States (Day 19)

This is a 100 Days challenge to learn a new language (Python). 100 Days of Code - The Complete Python Pro Bootcamp 

I will post some notes to motivate myself to finish this challenge.

Higher Order Functions

Can a function be passed to another function as an input?

A function is called Higher Order Function if it contains other functions as a parameter or returns a function as an output i.e, the functions that operate with another function are known as Higher Order Functions. Reference

Ex:

# Normal Function

def add(num_1, num_2):

    """add"""

    return num_1 + num_2

# Normal Function

def subtract(num_1, num_2):

    """subtract"""

    return num_1 - num_2

# This is a Higher Order Function

def calculator(num_1, num_2, func):

    """calculator"""

    return func(num_1, num_2)

# Call calculator func and pass add func as an input

# Notice that there is no () after 'add'

result = calculator(1, 2, add)

print(result)

Event Listener in Turtle Graphics 

Using Event Listener of Turtle Graphics to practice how to pass a function as an input.

Ex: Make turtle can move forward and back, and turn left and right

# Import Turtle and Screen Class from turtle module

from turtle import Turtle, Screen

def move_up():

    my_turtle.setheading(90)

    my_turtle.forward(50)

def move_down():

    my_turtle.setheading(270)

    my_turtle.forward(50)

def move_right():

    my_turtle.setheading(0)

    my_turtle.forward(50)

def move_left():

    my_turtle.setheading(180)

    my_turtle.forward(50)

# Get Screen Instance

screen = Screen()

# Bind each functions to key-release event

# of 'Up', 'Down', 'Right' and 'Left' key

screen.onkey(move_up, "Up")

screen.onkey(move_down, "Down")

screen.onkey(move_right, "Right")

screen.onkey(move_left, "Left")

# Set focus on TurtleScreen (in order to collect key-events)

screen.listen()

# Get turtle object

my_turtle = Turtle()

# Bind bye() method to mouse clicks on the Screen.

screen.exitonclick()

Instances and States

Since 'Turtle' class is a blueprint, we can build lots of turtle objects.

                object class

(instance 1)  my_turtle_1 = Turtle()

  (instance 2)  my_turtle_2 = Turtle()

Then in programming, we call my_turtle_1 and my_turtule_2 are separated instance.

Also, each instance (created by the same blueprint) maintains its own state.

my_turtle_1.shape('turtle')

my_turtle_2.shape('arrow')

Challenge - Race Game

Build a turtle race game, and allow users to guess which turtle will win the race?

import random

from turtle import Turtle, Screen

# Get Screen Instance

screen = Screen()

# Pop up a dialog window for input of a number

user_guess = screen.textinput(

    "Guess",

    "Which Turtle will win this race? input color

(red, orange, yellow, green and blue):",

)

turtles = []

colors = ["red", "orange", "yellow", "green", "blue"]

y_positions = [-100, -50, 0, 50, 100]

# Init all turtles

for index in range(0, 5):

    my_turtle = Turtle()

    my_turtle.shape("turtle")

    my_turtle.speed("fastest")

    my_turtle.color(colors[index])

    my_turtle.penup()

    my_turtle.setpos(-250, y_positions[index])

    turtles.append(my_turtle)

game_end = False

while not game_end:

    # make all turtles run randomly

    for index in range(0, 5):

        turtles[index].forward(random.randint(10, 50))

    # terminate race game if at lease one turtle reach finished line

    for index in range(0, 5):

        if turtles[index].xcor() > 250:

            game_end = True

# Custom sorting function to determine the sorting criteria

def my_sort(item):

    """my_sort"""

    return item.xcor()

# Sorting turtles list based on a custom function

# The fastest turtle will be the first element in this list after sorting

turtles.sort(reverse=True, key=my_sort)

# Checking the guess result

if user_guess == turtles[0].pencolor():

    print("You win")

else:

    print(f"You lose, the winner is the {turtles[0].pencolor()} turtle")

# Bind bye() method to mouse clicks on the Screen.

screen.exitonclick()