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Let’s Explore the difference between class methods and instance methods in the Python.

In Python, class methods and instance methods are two types of methods that serve different purposes and have different behaviors regarding how they access the data and functionality of a class and its instances.

What are instance Methods?

Instance methods are operate on an instance of the class. When creating an instance method, the first parameter is always self. self is (usually) passed hiddenly when calling an instance method.They can freely access and modify the state of an object (its attributes) because they receive the object instance (self) as their first parameter.

class User:  
    # constructor  
    def __init__(self, name, lastName):  
        # Instance variable  
        self.name = name  
        self.lastName= lastName
  
    # instance method to access instance variable  
    def userDetails(self):  
        print('Name:', self.name, 'LastName:', self.lastName); 
        
instance = User("John", "Susa");
instance.userDetails();

When to use instance method.

• If the method needs to access or modify instance-specific data (attributes), you should use an instance method.
• When the method performs operations that are relevant only to individual instances of the class.
• Use instance methods to encapsulate behavior associated with an object, ensuring that the object itself manages its state and behavior.

What are class Methods?

Class methods are methods that are bound to the class itself, not to the instances of the class. They can’t access specific instance data unless it is passed to them. class methods are very similar to an instance method, only difference is that instead of passing the instance hiddenly as a first parameter, we’re now passing the class itself as a first parameter. They work with class variables (attributes that are the same for every instance of the class) and can modify the class state that applies across all instances.

class User:  
    # Class Variable
    roll = "Admin"
    # constructor  
    def __init__(self, name, lastName):  
        # Instance variable  
        self.name = name  
        self.lastName= lastName
  
    # Class method to access Class variable  
    def change_roll(cls, roll): 
        cls.roll = roll;
        print('Roll:', cls.roll) 
        
instance = User("John", "Susa");
instance.change_roll("Adviser");

When to use Class Methods.

• If the method needs to access or modify class-level data (class variables), a class method is appropriate.
• Class methods are commonly used as factory methods that create instances of the class using specific parameters or initialization logic.
• When you want to provide alternative ways to create instances of a class or to customize the instantiation process.
• If the method provides functionality that’s relevant to the class as a whole, rather than to individual instances, consider using a class method.
• Class methods can be used in inheritance hierarchies to provide overridden behavior across subclasses.