Functions

Function ek named, reusable code ka block hai. Jahan bhi aap apne aap ko similar code ek se zyada baar likhte hue paao, usually yeh sign hai ki use function bana dena chahiye.

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))
print(greet("Bob"))

Hello, Alice!
Hello, Bob!

• def ek function definition start karta hai, uske baad uska naam aur parentheses mein parameters aate hain
• return ek value wapas bhej deta hai jahan se function call hua tha — iske bina, function None return karta hai
• name ek parameter hai — ek placeholder jo function call karte waqt jo bhi pass karo usse fill ho jaata hai

Default arguments

Aap ek parameter ko default value de sakte ho, jisse woh optional ban jaata hai — callers use poori tarah chhod bhi sakte hain, ya jab kuch alag chahiye to override kar sakte hain.

def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"

print(greet("Alice"))
print(greet("Bob", "Hi"))

Hello, Alice!
Hi, Bob!

Aage: lambda functions — chhote, ek line mein likhe throwaway functions.