OOP – Encapsulation and Properties

Private attributes, getters/setters, @property decorator, and data hiding.

Encapsulation

Encapsulation hides the internal state of an object and exposes only what is necessary. Python uses naming conventions rather than strict access modifiers:

• _name — "protected" by convention (one underscore).
• __name — "private", name-mangled by Python (two underscores).

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance     # private

    def deposit(self, amount):
        if amount > 0:
            self.__balance += amount

    def get_balance(self):
        return self.__balance

acc = BankAccount(1000)
acc.deposit(500)
print(acc.get_balance())  # 1500

Properties with @property

The @property decorator lets you access methods like attributes and add validation:

class Circle:
    def __init__(self, radius):
        self._radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, value):
        if value < 0:
            raise ValueError("Radius cannot be negative")
        self._radius = value

    @property
    def area(self):
        import math
        return math.pi * self._radius ** 2

c = Circle(5)
print(c.area)     # 78.53...
c.radius = 10    # uses setter