Codexpal - Learn Programming Interactively

Lesson Content

Making Decisions: Conditional Statements

Conditional statements allow your program to make decisions and execute different code based on conditions. This is fundamental to programming!

The if Statement

Execute code only if a condition is True:

age = 18
if age >= 18:
    print("You are an adult")

The if-else Statement

Execute one block if True, another if False:

age = 15
if age >= 18:
    print("You are an adult")
else:
    print("You are a minor")

The if-elif-else Statement

Check multiple conditions:

score = 85
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"
print(f"Your grade is {grade}")

Comparison Operators Review

# Equal to
if x == 5:
    print("x is 5")

# Not equal to
if x != 5:
    print("x is not 5")

# Greater than
if x > 10:
    print("x is greater than 10")

# Less than
if x < 10:
    print("x is less than 10")

# Greater than or equal
if x >= 10:
    print("x is 10 or more")

# Less than or equal
if x <= 10:
    print("x is 10 or less")

Logical Operators

Combine multiple conditions:

age = 25
has_license = True

# AND - both must be True
if age >= 18 and has_license:
    print("You can drive")

# OR - at least one must be True
if age < 18 or age > 65:
    print("Special pricing available")

# NOT - reverses the condition
if not has_license:
    print("You need a license")

Nested Conditionals

Conditionals inside conditionals:

age = 20
has_ticket = True

if age >= 18:
    if has_ticket:
        print("Welcome to the event!")
    else:
        print("You need a ticket")
else:
    print("You must be 18 or older")

Common Patterns

# Check if number is positive, negative, or zero
number = 5
if number > 0:
    print("Positive")
elif number < 0:
    print("Negative")
else:
    print("Zero")

# Check if string is empty
text = ""
if text:
    print("Text has content")
else:
    print("Text is empty")

Example Code

Create a program that assigns a grade based on a score.

# Grade Calculator
# Score >= 90: A
# Score >= 80: B
# Score >= 70: C
# Score >= 60: D
# Otherwise: F

score = 85

# Your code here:
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "F"

print(f"Score: {score}, Grade: {grade}")

Expected Output:

Score: 85, Grade: B

Study Tips

•Read the theory content thoroughly before practicing
•Review the example code to understand key concepts
•Proceed to the Practice tab when you're ready to code

Conditional Statements (if/else)