100 Days Of Python - Day 17

Day 17

Creating Classes

• Classes are blueprints for creating new objects.
• If the class name is has more than one word, it is written in PascalCase.
• The syntax for creating a class is:

class ClassName:

• If a class has no methods, it can be created with the pass keyword. This is useful when you want to create a class but don’t want to add any methods to it yet.

class ClassName:
    pass

Creating Objects

• Objects are instances of a class.
• If the object name is has more than one word, it is written in snake_case.
• The syntax for creating an object is:

object_name = ClassName()

Adding Attributes to Objects

• Attributes are variables that belong to an object.
• Attributes are added to an object using the dot notation.
• The syntax for adding an attribute to an object is:

object_name.attribute_name = value

# Example
car.color = "red"

Adding Attributes to Classes

• Attributes can be added to a class using the __init__() method.
• The __init__() method is called when an object is created.
• It is also called the constructor method.
• The __init__() method is used to initialize the attributes of an object.

class ClassName:
    def __init__(self, attribute1, attribute2):
        self.attribute1 = attribute1
        self.attribute2 = attribute2

# Example
class Car:
    def __init__(self, color, mileage):
        self.color = color
        self.mileage = mileage

car = Car("blue", 20000)
print(car.color)
print(car.mileage)

# Output:
# blue
# 20000

• The self keyword refers to the current object.

class User:
    def __init__(self, user_id, username):
        self.id = user_id
        self.username = username

user_1 = User("001", "Aretas")
print(user_1.id)
print(user_1.username)

# Output:
# 001
# Aretas

• defaulf values can be set for attributes in the __init__() method.

class User:
    def __init__(self, user_id, username, email):
        self.id = user_id
        self.username = username
        self.email = email
        self.followers = 0
        self.following = 0

Adding Methods to Classes

• Methods are functions that belong to a class.
• Methods are added to a class using the dot notation.
• The syntax for adding a method to a class is:

class ClassName:
    def method_name(self):
        # code goes here

# Example
class Car:
    def __init__(self, color, mileage):
        self.color = color
        self.mileage = mileage

    def drive(self, miles):
        self.mileage += miles

car = Car("blue", 20000)
print(car.mileage)
car.drive(100)
print(car.mileage)

# Output:
# 20000
# 20100

• The self keyword refers to the current object.

class User:
    def __init__(self, user_id, username, email):
        self.id = user_id
        self.username = username
        self.email = email
        self.followers = 0
        self.following = 0

    def follow(self, user):
        user.followers += 1
        self.following += 1