Day 21
Class Inheritance
Inheritance
- Inheritance is a way to create a new class from an existing class.
- The new class is called the child class and the existing class is called the parent class.
- The child class inherits all of the attributes and methods of the parent class.
- The child class can also have its own attributes and methods.
- The child class can also override the attributes and methods of the parent class.
- The child class can also add new attributes and methods to the parent class.
Creating a Child Class
- To create a child class, we pass the parent class as an argument to the child class.
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| class ChildClass(ParentClass):
# Child class code
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- For example, we can create a
Fish
class that inherits from the Animal
class.
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| class Fish(Animal):
# Fish class code
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- The
Fish
class will inherit all of the attributes and methods of the Animal
class. - We can then add new attributes and methods to the
Fish
class.
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| class Animal:
def __init__(self):
self.eyes = 2
self.legs = 4
def breathe(self):
print("The animal is breathing.")
def eat(self):
print("The animal is eating.")
class Fish(Animal):
def __init__(self):
super().__init__()
self.fins = 2
def swim(self):
print("The fish is swimming.")
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- The
Fish
class has a new attribute called fins
and a new method called swim()
. - The
Fish
class also has all of the attributes and methods of the Animal
class. - The
super()
function is used to call the __init__()
method of the parent class. This allows us to use the attributes and methods of the parent class in the child class.
Overriding Methods
- We can override the methods of the parent class in the child class.
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| class Fish(Animal):
def __init__(self):
super().__init__()
self.fins = 2
def swim(self):
print("The fish is swimming.")
def breathe(self):
print("The fish is breathing through its gills.")
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- The
Fish
class overrides the breathe()
method of the Animal
class. - The
Fish
class has a new breathe()
method that prints βThe fish is breathing through its gills.β
Slicing Lists
Slicing Lists
- We can use slicing to get a subset of a list.
- We can use slicing to get a subset of a list from a starting index to an ending index.
- We can also use slicing to get a subset of a list from a starting index to an ending index with a step size.
- We can also use slicing to get a subset of a list from a starting index to an ending index with a step size in reverse order.
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| # Get a subset of a list from a starting index to an ending index
list[start:end]
# Get a subset of a list from a starting index to an ending index with a step size
list[start:end:step]
# Get a subset of a list from a starting index to an ending index with a step size in reverse order
list[start:end:-step]
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- The starting index is inclusive.
- The ending index is exclusive.
- The step size is the number of elements to skip.
- The step size can be negative to go in reverse order.
For example, we can use slicing to get a subset of a list from a starting index to an ending index.
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| numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# Get a subset of a list from a starting index to an ending index
print(numbers[2:5])
# Output: [3, 4, 5]
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- The starting index is 2.
- The ending index is 5.
We can also use slicing to get a subset of a list from a starting index to an ending index with a step size.
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| numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# Get a subset of a list from a starting index to an ending index with a step size
print(numbers[2:8:2])
# Output: [3, 5, 7]
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- The starting index is 2.
- The ending index is 8.
- The step size is 2.
We can also use slicing to get a subset of a list from a starting index to an ending index with a step size in reverse order.
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| numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# Get a subset of a list from a starting index to an ending index with a step size in reverse order
print(numbers[8:2:-2])
# Output: [9, 7, 5]
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- The starting index is 8.
- The ending index is 2.
The step size is -2.
- Slicing also works with Tuple and String objects. For example:
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| # Slicing a Tuple
tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
# Get a subset of a tuple from a starting index to an ending index
print(tuple[2:5])
# Output: (3, 4, 5)
# Get a subset of a tuple from a starting index to an ending index with a step size
print(tuple[2:8:2])
# Output: (3, 5, 7)
# Get a subset of a tuple from a starting index to an ending index with a step size in reverse order
print(tuple[8:2:-2])
# Output: (9, 7, 5)
# Slicing a String
string = "Hello World"
# Get a subset of a string from a starting index to an ending index
print(string[2:5])
# Output: llo
# Get a subset of a string from a starting index to an ending index with a step size
print(string[2:8:2])
# Output: loW
# Get a subset of a string from a starting index to an ending index with a step size in reverse order
print(string[8:2:-2])
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Snake Game Part 2
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| from turtle import Turtle
import random
class Food(Turtle):
def __init__(self):
super().__init__()
self.shape("circle")
self.penup()
self.shapesize(stretch_len=0.5, stretch_wid=0.5)
self.color("blue")
self.speed("fastest")
self.refresh()
def refresh(self):
random_x = random.randint(-280, 280)
random_y = random.randint(-280, 280)
self.goto(random_x, random_y)
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| from turtle import Turtle
STARTING_POSITIONS = [(0, 0), (-20, 0), (-40, 0)]
MOVE_DISTANCE = 20
UP = 90
DOWN = 270
LEFT = 180
RIGHT = 0
class Snake:
def __init__(self):
self.segments = []
self.create_snake()
self.head = self.segments[0]
def create_snake(self):
for position in STARTING_POSITIONS:
self.add_segment(position)
def add_segment(self, position):
new_segment = Turtle("square")
new_segment.color("white")
new_segment.penup()
new_segment.goto(position)
self.segments.append(new_segment)
def extend(self):
# Add a new segment to the snake
self.add_segment(self.segments[-1].position())
def move(self):
# Move the snake
for seg_num in range(len(self.segments) - 1, 0, -1):
new_x = self.segments[seg_num - 1].xcor()
new_y = self.segments[seg_num - 1].ycor()
self.segments[seg_num].goto(new_x, new_y)
self.segments[0].forward(MOVE_DISTANCE)
def up(self):
if self.head.heading() != DOWN:
self.head.setheading(UP)
def down(self):
if self.head.heading() != UP:
self.head.setheading(DOWN)
def left(self):
if self.head.heading() != RIGHT:
self.head.setheading(LEFT)
def right(self):
if self.head.heading() != LEFT:
self.head.setheading(RIGHT)
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| from turtle import Turtle
ALIGNMENT = "center"
FONT = ("Roboto", 24, "normal")
# Create a scoreboard class that inherits from the Turtle class
class Scoreboard(Turtle):
# Create a constructor method that inherits from the Turtle class
def __init__(self):
super().__init__()
# Create a score attribute
self.score = 0
# Create a high score attribute
self.high_score = 0
# Create a scoreboard object
self.penup()
# Hide the scoreboard object
self.hideturtle()
# Move the scoreboard object to the top of the screen
self.goto(0, 270)
# Change the color of the scoreboard object
self.color("white")
# Update the scoreboard object
self.update_scoreboard()
# Update the scoreboard object
def update_scoreboard(self):
# Clear the scoreboard object
self.clear()
# Write the score on the scoreboard object
self.write(f"Score: {self.score} High Score: {self.high_score}", align=ALIGNMENT, font=FONT)
# Reset the scoreboard object
def reset(self):
# Check if the score is greater than the high score
if self.score > self.high_score:
# Set the high score to the score
self.high_score = self.score
# Set the score to 0
self.score = 0
# Update the scoreboard object
self.update_scoreboard()
# Increase the score by 1
def increase_score(self):
# Increase the score by 1
self.score += 1
# Update the scoreboard object
self.update_scoreboard()
# Game over
def game_over(self):
# Move the scoreboard object to the center of the screen
self.goto(0, 0)
# Write the score on the scoreboard object
self.write("GAME OVER", align=ALIGNMENT, font=FONT)
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| from turtle import Screen
from snake import Snake
from food import Food
from scoreboard import Scoreboard
import time
screen = Screen()
screen.setup(width=600, height=600)
screen.bgcolor("black")
screen.title("Snake Game")
screen.tracer(0)
snake = Snake()
food = Food()
scoreboard = Scoreboard()
screen.listen()
screen.onkey(snake.up, "Up")
screen.onkey(snake.down, "Down")
screen.onkey(snake.right, "Right")
screen.onkey(snake.left, "Left")
# Move the snake
game_is_on = True
while game_is_on:
screen.update()
time.sleep(0.1)
snake.move()
# Detect collision with food
if snake.head.distance(food) < 15:
food.new_food()
snake.extend()
scoreboard.increase_score()
# Detect collision with wall
if snake.head.xcor() > 280 or snake.head.xcor() < -290 or snake.head.ycor() > 290 or snake.head.ycor() < -280:
game_is_on = False
scoreboard.game_over()
# Detect collision with tail
for segment in snake.segments[1:]:
if snake.head.distance(segment) < 10:
game_is_on = False
scoreboard.game_over()
# Exit the screen
screen.exitonclick()
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