Classes

What is a Class?

A class in Python is a blueprint for creating objects. Objects represent real-world entities with properties (attributes) and actions (methods). Using classes, you can organize and reuse code efficiently.

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Why Use Classes?

• To group related data and functions together.

• To create multiple objects with similar structure but different data.

• To model real-world things (like students, cars, animals) in code.

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Defining a Simple Class

Here is how you define a basic class in Python:

class Person:
    pass

The pass statement means "do nothing". This class doesn't do anything yet.

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Adding Attributes

Attributes are variables that belong to the object. You define them using a special method called __init__.

class Person:
    def __init__(self, name, age):
        self.name = name  # attribute
        self.age = age    # attribute

• __init__: This is called the constructor. It runs when you create a new object.

• self: Refers to the current object being created.

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Creating Objects (Instances) from a Class

You can create objects by calling the class like a function:

person1 = Person("Alice", 22)
person2 = Person("Bob", 30)

print(person1.name)  # Output: Alice
print(person2.age)   # Output: 30

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Adding Methods

Methods are functions defined inside a class. They describe what objects can do.

class Person:
    def __init__(self, name):
        self.name = name

    def greet(self):
        print("Hello, my name is", self.name)

person1 = Person("Alice")
person1.greet()  # Output: Hello, my name is Alice

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Example: A Simple Student Class

class Student:
    def __init__(self, name, student_id):
        self.name = name
        self.student_id = student_id

    def show_info(self):
        print(f"Name: {self.name}, ID: {self.student_id}")

student1 = Student("John", 12345)
student1.show_info()  # Output: Name: John, ID: 12345

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Summary

• Class: A blueprint for objects.

• Object: An instance of a class.

• Attributes: Variables that belong to an object.

• Methods: Functions that belong to an object.

• Use __init__ to set up initial values.

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Practice

Try writing your own class, for example, a Car class with attributes like make and year, and a method to display information.