Conditional Statements (if, elif, else)

Every program eventually needs to do different things depending on a value. Python uses if, elif (short for "else if"), and else for this — and instead of curly braces, it uses indentation to mark what belongs inside each block.

age = 20
if age >= 18:
    print("You are an adult")
else:
    print("You are a minor")

You are an adult

That indentation isn't just a style choice — it's how Python knows what belongs inside the if block. Get it wrong (mix tabs and spaces, or indent inconsistently) and you'll get a real IndentationError, not a silent bug.

Chaining conditions with elif

score = 75
if score >= 90:
    print("A")
elif score >= 80:
    print("B")
elif score >= 70:
    print("C")
else:
    print("F")

C

Python checks each condition top to bottom and stops at the first one that's true — score >= 70 matches before it ever reaches else, so "C" is printed and everything after is skipped.

Next: for loops — repeating code over every item in a collection.