Conditionals (if / elif / else)

~30 min

1. Program Branching: Making Decisions

By default, computer programs execute linearly, line by line. To create smart applications, we must let programs make decisions. Python uses if, elif (else-if), and else keywords to evaluate statements and branch code execution accordingly. A conditional statement evaluates to a Boolean value (True or False). Python uses indentations (4 spaces) rather than brackets to mark blocks of code under each branch.

2. Comparison Operators

Comparison operators are used to compare two values, yielding a Boolean output:

== Equal to (Note: = is for assignment, == is for comparison!)
!= Not equal to
< Less than | > Greater than
<= Less than or equal to | >= Greater than or equal to

temperature = 22

if temperature > 30:
    print("It's a hot day!")
elif temperature >= 15:
    print("It's a pleasant day.")
else:
    print("It's a cold day.")

3. Logical Operators: and, or, not

Logical operators allow you to combine multiple conditional statements or invert them:

and: Returns True if both conditions are True.
or: Returns True if at least one condition is True.
not: Inverts the Boolean state (returns True if the condition is False).

age = 20
has_ticket = True
is_vip = False

# Both must be True
if age >= 18 and has_ticket:
    print("Allowed entry")

# Either can be True
if has_ticket or is_vip:
    print("Welcome inside")

4. Common Beginner Mistakes

⚠️ Watch out for these mistakes:

Missing Colon: Forgetting the : at the end of if, elif, or else. This causes a SyntaxError.
Single '=' for Comparison: Writing if score = 100: instead of if score == 100:. This is a syntax error because = assigns variables.
Indentation Errors: Failing to indent the code blocks under the conditional statement or mixing spaces and tabs. Ensure exactly 4 spaces.

Your code

Check when done Program prompts for an age and converts it to integer Uses if, elif, and else branches Correctly outputs $5, $10, or $7 based on input age

1. Which operator is used to check if two values are equal in Python?

= == equals

2. What is the output of `print(True or False)`?

True False

3. What happens if you skip indenting the code inside an `if` block?

It executes normally but ignores the check It crashes immediately with an IndentationError It runs but prints a warning message

🚀 Progression

Decisions are completed. Next, you'll learn how to repeat actions efficiently using **Loops**.