Lesson — OOP

DABBE KE
ANDAR DABBA.

Order ke andar Item, Laptop ke andar Battery — part-of rishte ke liye inner class. Simple, saaf, MNC-approved pattern.

WHY: dabbe ke andar dabba

Swiggy Order ke andar Item hote hain — item ka matlab order ke bina adhoora hai. Aise has-a, part-of rishte ke liye class ke andar class: inner class.

class Order:
    def __init__(self, oid):
        self.oid = oid
        self.items = []
    class Item:
        def __init__(self, name, price):
            self.name = name
            self.price = price

o = Order("SW-1")
o.items.append(Order.Item("Dosa", 120))
print(o.items[0].price)  # 120

HOW: andar wali class

Inner class normal class jaisi hi — bas outer ke naam ke neeche rehti hai. Bahar se Outer.Inner() likhkar banao. Simple rakho: 1 level nesting kaafi hai.

class Laptop:
    class Battery:
        def __init__(self):
            self.pct = 100
    def __init__(self):
        self.bat = Laptop.Battery()

print(Laptop().bat.pct)  # 100

Common mistakes

• Bina wajah nesting — flat code pehle, inner jab rishta part-of ho.
• Item() seedha banana — bahar se Order.Item() likho.
• Inner ko outer ka data auto-milega samajhna — explicitly pass karo.