Chapter 4: Python Control Flow

if, else, elif Statements & Nested Conditions

1. if Statement

Kya karta hai: Yeh condition ko check karta hai aur agar condition true hoti hai, to block of code execute hota hai.

Rule: Condition ko sahi likhna zaroori hai, agar galat likha to statement execute nahi hoga.
# if statement example age = 20 if age >= 18: print("You are an adult.")
You are an adult.
# if statement example with wrong condition age = 15 if age >= 18: print("You are an adult.") else: print("You are not an adult.")
You are not an adult.

2. else Statement

Kya karta hai: Yeh default block hota hai jo else ke baad likha jata hai, jab condition false hoti hai.

Rule: Else statement ko tabhi use karo jab condition fail ho jaaye.
# else statement example age = 15 if age >= 18: print("You are an adult.") else: print("You are not an adult.")
You are not an adult.

3. elif Statement

Kya karta hai: Yeh else aur if ka combination hota hai. Jab ek se zyada conditions check karni hoti hain to elif ka use hota hai.

Rule: elif ko tab use karo jab ek hi time pe multiple conditions check karni ho.
# elif statement example age = 25 if age < 18: print("You are a child.") elif age < 30: print("You are a young adult.") else: print("You are an adult.")
You are a young adult.

4. Nested Conditions

Kya karta hai: Jab ek condition ke andar doosri condition likhi jaati hai, to usse nested condition kehte hain.

Rule: Nested conditions ko tab use karo jab complex decision making ho.
# Nested if statement example age = 25 if age >= 18: if age < 30: print("You are a young adult.") else: print("You are an adult.") else: print("You are not an adult.")
You are a young adult.