Conditional statements in Python: if, elif, and else

Every program you’ve written so far works exactly the same every time you run it. It doesn’t matter what data you enter, doesn’t matter what happens: the code always follows the same path, top to bottom, no detours.

That’s fine for a calculator script. But real programs need to react. An online store that shows the same price to everyone regardless of whether they have a discount isn’t very useful. A fitness app that tells you to exercise even when you’ve already done it isn’t either.

The ability to make decisions is what separates a rigid program from one that does something interesting. And in Python, that ability is called control flow.

What is a conditional statement?

Think about how you make decisions in real life. “If it’s raining, grab an umbrella. If it’s not, go out normally.” That’s exactly what an if does in Python: it runs a block of code only when a condition is met.

The basic structure looks like this:

if condition:
    # This code runs only if the condition is True
    print("The condition is met")

Two important things before we continue:

The colon (:): it’s mandatory at the end of the if line. Forget it and Python will throw a SyntaxError without mercy.

Indentation: the block of code inside the if must be indented — typically 4 spaces. In Python, indentation isn’t optional or decorative. It’s part of the syntax. Without it, the code doesn’t belong to the if.

age = 20

if age >= 18:
    print("You are an adult")    # Inside the if — runs if True
    print("You can vote")        # Also inside — same indentation

print("This always shows up")    # Outside the if — always runs

If age is 20, you’ll see all three messages. If age were 15, you’d only see the last one.

The else: plan B

What if you want to do something different when the condition isn’t met? That’s what else is for. It works like the “otherwise” in everyday speech:

temperature = 35

if temperature > 30:
    print("It's hot, stay inside")
else:
    print("Pleasant temperature, go for a walk")

else carries no condition — it simply catches all the cases the if didn’t cover. If the if condition is True, the if block runs and else is ignored. If it’s False, the opposite happens.

One important thing: else always pairs with an if. You can’t have a standalone else. Python would complain, and rightly so.

The elif: when there are more than two options

Life is rarely binary. Sometimes you need to evaluate multiple conditions in order, until you find one that’s true. That’s where elif comes in — short for “else if”:

grade = 72

if grade >= 90:
    print("A — Excellent")
elif grade >= 80:
    print("B — Good")
elif grade >= 70:
    print("C — Average")
elif grade >= 60:
    print("D — Passing")
else:
    print("F — Fail")

C — Average

The evaluation order is top to bottom. Python checks the first condition; if it’s False, it moves to the next elif; if that’s also False, to the next one… until one is True or it reaches the else. As soon as it finds a true condition, it runs that block and exits. It doesn’t keep checking the rest.

This means order matters. A lot. Look at what happens if we mix up the conditions:

grade = 95

# ⚠️ Wrong order — will never reach the higher grades
if grade >= 60:
    print("D — Passing")    # This runs for 95... not what we wanted
elif grade >= 70:
    print("C — Average")
elif grade >= 80:
    print("B — Good")
elif grade >= 90:
    print("A — Excellent")

D — Passing

A grade of 95 classified as passing. The problem: 95 >= 60 is True, so Python runs that block and never reaches the 90 condition. The general rule: most restrictive first, most permissive last.

Truth and falsiness in Python

Python has a pretty flexible view of what it considers true and what it considers false. Any value can be used as a condition, not just True and False:

# These are "falsy" — Python treats them as False in a condition
if 0:
    print("This never shows")

if "":
    print("Neither does this")

if []:
    print("An empty list either")

if None:
    print("None either")

# These are "truthy" — any non-empty, non-zero value
if 42:
    print("A non-zero number: truthy")

if "hello":
    print("A non-empty string: truthy")

if [1, 2, 3]:
    print("A list with elements: truthy")

This comes in handy. Instead of writing if len(my_list) > 0, you can just write if my_list. Python knows an empty list is “false” and one with elements is “true”.

name = input("What's your name? ")

if name:
    print(f"Hello, {name}!")
else:
    print("You didn't enter your name")

Clean, direct, readable.

Compound conditions

You already know how to use and, or, and not from the previous lesson. Now it all makes sense inside an if:

age = 25
has_license = True

if age >= 18 and has_license:
    print("You can rent a car")
else:
    print("You don't meet the requirements")

day = "Saturday"

if day == "Saturday" or day == "Sunday":
    print("It's the weekend, time to rest")
else:
    print("Back to work")

is_premium = False

if not is_premium:
    print("Go premium to access this content")

A condition with and is only true if all sub-conditions are true. With or, it’s enough for one to be true. With not, you invert the result.

Nested conditionals: with care

It’s perfectly valid to put an if inside another if. These are called nested conditionals:

age = 20
has_ticket = True

if age >= 18:
    if has_ticket:
        print("You can enter the concert")
    else:
        print("You're old enough but you need a ticket")
else:
    print("You can't enter, you're underage")

It works, but use them sparingly. Every nesting level adds complexity and makes the code harder to read. If you find yourself three if levels deep, you can probably simplify with and:

# ✅ Cleaner with and
if age >= 18 and has_ticket:
    print("You can enter the concert")
elif age >= 18:
    print("You're old enough but you need a ticket")
else:
    print("You can't enter, you're underage")

The unwritten rule: if you can avoid nesting, avoid it.

A program that makes real decisions

Let’s put everything together in a concrete example. A library access system that checks multiple conditions:

age = int(input("How old are you? "))
has_card = input("Do you have a library card? (y/n) ") == "y"
books_on_loan = int(input("How many books do you currently have on loan? "))

print()  # Empty line for readability

if age < 6:
    print("Sorry, you need to be at least 6 years old to use the library.")
elif not has_card:
    print("You need a library card. You can get one at the reception desk.")
elif books_on_loan >= 5:
    print("You've reached the loan limit. Return a book before borrowing more.")
else:
    print("Welcome! You can borrow books.")
    if books_on_loan >= 3:
        print("Remember, you only have", 5 - books_on_loan, "loans remaining.")

Notice the structure: we check the cases that block access first, and leave the successful case for the else. This is a common pattern called early exit — filtering out the negative cases upfront so the main flow stays clean at the end.

Summary

• if condition: runs a block only if the condition is true
• elif chains alternative conditions; Python evaluates top to bottom and stops at the first true one
• else catches all cases that didn’t match any previous condition
• Indentation (4 spaces) isn’t decorative — it defines which code belongs to which block
• Python has truthiness: values like 0, "", [], and None evaluate as False
• Nested conditionals work, but and / or are usually cleaner

---

With conditional statements, your programs can finally make decisions. But decisions alone aren’t enough — often you need to repeat an action a certain number of times, or as long as a condition holds. In the next tutorial you’ll learn while loops: how to make Python repeat code automatically, and why you need to watch out for infinite loops.

Never stop coding!

---

💡 Challenge: Write a program that asks the user for a numeric grade from 0 to 10 and displays the letter grade (A, B, C, D, F). Add validation: if the user enters a number outside the 0–10 range, show an error message instead of trying to classify it. Bonus: what happens if they enter a negative number? What if they enter text instead of a number?