Decision-Making in Python: Mastering if, elif, and else

In programming, it’s not enough to just perform calculations or store data — we often need our programs to respond to different situations. In other words:

“If something happens, do this. Otherwise, do something else.”

Python provides a simple but powerful way to handle this using decision-making logic with the keywords if, elif, and else.

1. What is an if statement?

The if statement allows your program to run a block of code only when a specific condition is true.

number = 10

if number > 0:
    print("The number is positive.")        

Output:

The number is positive.        

If number = -5, the code inside the if block would be skipped entirely.

Python automatically evaluates conditions like number > 0 as True or False.

2. What if the condition is not true? (else)

The else block provides an alternative action when the if condition is false.

number = -3

if number > 0:
    print("The number is positive.")
else:
    print("The number is zero or negative.")        

Output:

The number is zero or negative.        

3. Handling multiple options: elif

elif stands for "else if" and lets you test multiple conditions in sequence. You can use as many elif branches as you like, but only one else.

score = 72

if score >= 90:
    print("Excellent!")
elif score >= 70:
    print("Very good.")
elif score >= 50:
    print("Satisfactory.")
else:
    print("Failed.")        

Output:

Very good.        

Python runs only the first true condition – all others are skipped.

4. Combining conditions: and, or, not

Sometimes you want to evaluate multiple conditions at once. You can use logical operators:

age = 20
has_ticket = True

if age >= 18 and has_ticket:
    print("Access granted.")
else:
    print("Access denied.")        

and – both conditions must be true

or – at least one condition must be true

not – inverts the condition (not True becomes False)

5. Indentation matters in Python!

Unlike many other languages, Python does not use curly braces {} to define code blocks. Instead, it uses indentation (spaces or tabs).

x = 10

if x > 5:
    print("Greater than 5")
    print("Still inside the if block")
print("Outside the condition")        

Incorrect indentation will result in an error:

if True:
print("Error!")  # ❌ IndentationError        

6. Nested conditions – decisions inside decisions

You can place one condition inside another to create more precise logic:

age = 25
is_student = True

if age >= 18:
    if is_student:
        print("Adult student")
    else:
        print("Adult non-student")
else:
    print("Minor")        

Output:

Adult student        

7. You don't always need else

It’s totally fine to use just an if when you only care about a single situation:

language = "Python"

if language == "Python":
    print("This is our favorite language!")        

No else is needed if there's nothing to handle otherwise.

8. Common mistakes and how to avoid them

❌ Using = instead of ==:

if x = 5:  # Error!        

✅ Use:

if x == 5:        

❌ Incorrect indentation:

if x > 5:
print("Wrong")         

✅ Use:

if x > 5:
    print("Correct")        

❌ Forgetting the colon :

if x > 5  # Missing colon!        

✅ Use:

if x > 5:        

Summary

• if checks a condition and runs code if it's true
• elif adds more possible conditions
• else handles everything that didn’t match
• You can combine conditions with and, or, and not
• Python uses indentation, not curly braces, to define code blocks
• Conditions can be nested for more complex logic