@classmethod

Can only access class-level stuff, not with the object
The first argument is always cls (like self, but for class)
Used when you want to access or modify class-level stuff

Bank Analogy:

Suppose your bank gives a standard interest rate to all savings accounts

class BankAccount:
    interest_rate = 0.05  # class-level property

    @classmethod
    def update_interest_rate(cls, new_rate):
        cls.interest_rate = new_rate
        print(f"Updated interest rate to {cls.interest_rate}")

All accounts will get the new rate
No need to create an object to update it

How do I know it’s class level or object level?

If you write it inside the constructor (__init__), then it becomes an object-level property.

Each object will have its own copy of that property.

Example:

class BankAccount:
    def __init__(self, holder):
        self.holder = holder           # object-level
        self.interest_rate = 0.05      # object-level

Now self.interest_rate is tied to each object
You can change it for one object, it won’t affect others

But this one is class-level: because it is not written inside the constructor (__init__)

class BankAccount:
    interest_rate = 0.05  # class-level

This is shared among all objects
If you change it with cls.interest_rate, it updates for everyone

Simple Difference:

Defined where?	Belongs to?	Can access using?
Inside class (outside methods)	Class-level	Class name or `cls`
Inside constructor (`__init__`)	Object-level	Object name or `self`

@classmethod

Bank Analogy:

How do I know it’s class level or object level?

@classmethod → ✅ has logic → so it's a concrete method

`@classmethod` → ✅ has logic → so it's a concrete method