Class Methods in Python

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Class Methods in Python

Methods are functions defined inside a class.

They describe the actions or behavior of objects created from that class.

Each method automatically receives the current object through the self parameter.

Defining a Method in a Class

Methods are created just like functions, but they are placed inside a class.

Example: Simple Class Method

class User: def __init__(self, username): self.username = username def say_hello(self): print(f"Hi, I am {self.username}") u1 = User("Ananya") u1.say_hello()

Output:

Hi, I am Ananya

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Note: self must always be the first parameter of an instance method.

Methods with Parameters

Methods can accept additional parameters, just like normal functions.

Example: Method with Arguments

class MathTool: def subtract(self, x, y): return x - y def power(self, base, exp): return base ** exp tool = MathTool() print(tool.subtract(10, 4)) print(tool.power(2, 5))

Output:

6
32

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Methods Accessing Object Properties

Methods can read object data using self.

Example: Access Properties Inside a Method

class Profile: def __init__(self, name, country): self.name = name self.country = country def details(self): return f"{self.name} lives in {self.country}" p1 = Profile("Riya", "India") print(p1.details())

Output:

Riya lives in India

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Methods Modifying Object Properties

Methods can also update the values of object properties.

Example: Modify a Property

class Counter: def __init__(self, value=0): self.value = value def increment(self): self.value += 1 print(f"Current value: {self.value}") c1 = Counter() c1.increment() c1.increment()

Output:

Current value: 1
Current value: 2

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The __str__() Method

The __str__() method defines what should be displayed when an object is printed.

Example: Without __str__()

class Device: def __init__(self, name): self.name = name d1 = Device("Router") print(d1)

Output:

<__main__.Device object at 0x7f8b9a1c2d30>

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Example: With __str__()

class Device: def __init__(self, name): self.name = name def __str__(self): return f"Device Name: {self.name}" d1 = Device("Router") print(d1)

Output:

Device Name: Router

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Using Multiple Methods in a Class

A class can contain multiple methods that work together to perform tasks.

Example: Multiple Methods Working Together

class TaskList: def __init__(self): self.tasks = [] def add_task(self, task): self.tasks.append(task) print(f"Task added: {task}") def remove_task(self, task): if task in self.tasks: self.tasks.remove(task) def show_tasks(self): print("Tasks:") for t in self.tasks: print("-", t) todo = TaskList() todo.add_task("Study Python") todo.add_task("Practice OOP") todo.show_tasks()

Output:

Task added: Study Python
Task added: Practice OOP
Tasks:
- Study Python
- Practice OOP

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Deleting Methods from a Class

You can remove a method from a class using the del keyword. This affects all objects of that class.

This is rarely used in real-world programs.

Example: Delete a Class Method

class Demo: def show(self): print("Hello") obj = Demo() del Demo.show try: obj.show() except AttributeError as e: print(f"Error: {e}")

Output:

Error: 'Demo' object has no attribute 'show'

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