Python Basics — Day 5 Conditional Statements (if / elif / else)

1️⃣ Basic if Statement

• Code inside the block runs only if the condition is True.

age = 20

if age >= 18:
    print("You are an adult.")   # Condition is True → executed

⚠️ Note: Indentation matters! In Python, 4 spaces are recommended.

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2️⃣ if ~ else

If the condition is True, the if block runs. Otherwise, the else block runs.

age = 15

if age >= 18:
    print("You are an adult.")
else:
    print("You are a minor.")

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3️⃣ if ~ elif ~ else

Use elif to check multiple conditions in order.
Python executes only the first condition that is True.

score = 85

if score >= 90:
    print("Grade A")
elif score >= 80:
    print("Grade B")
elif score >= 70:
    print("Grade C")
else:
    print("Grade F")

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4️⃣ Nested if

You can place another if statement inside an existing one.

age = 20
is_student = True

if age >= 18:
    if is_student:
        print("You are an adult student.")
    else:
        print("You are an adult, but not a student.")

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5️⃣ Using Comparison & Logical Operators

You can combine conditions with and, or, and not.

temp = 25

if temp > 20 and temp < 30:
    print("The weather is warm.")

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6️⃣ Practice Examples

📝 Example 1: Even or Odd

num = int(input("Enter a number: "))

if num % 2 == 0:
    print("Even number")
else:
    print("Odd number")

📝 Example 2: Age Group

age = int(input("Enter your age: "))

if age < 13:
    print("Child")
elif age < 20:
    print("Teenager")
else:
    print("Adult")

📝 Example 3: Login Simulation

user_id = input("Username: ")
password = input("Password: ")

if user_id == "admin" and password == "1234":
    print("Login successful!")
else:
    print("Login failed!")

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