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Python Conditionals

Conditionals in Python allow you to make decisions in your code. They let your program behave differently based on different inputs or states.

The if Statement

The most basic conditional is the if statement. It runs a block of code only if the condition is True.

age = 18

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

if...else Statement

Use else to provide an alternative block of code when the condition is False.

age = 16

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

Comparison Operators

These are used to compare values and return a boolean (True or False).

Operator Meaning Example Result
== Equal to 5 == 5 True
!= Not equal to 5 != 3 True
> Greater than 7 > 3 True
< Less than 2 < 1 False
>= Greater or equal 3 >= 3 True
<= Less or equal 2 <= 5 True

Examples in Conditionals:

a = 10
b = 20

# Check for equality
if a == b:
    print("a and b are equal")
else:
    print("a and b are not equal")

# Check for ordering
if a < b:
    print("a is less than b")

# Combine comparison and action
if b >= 20:
    print("b is at least 20")

Logical Operators

Logical operators combine multiple conditions into a single boolean result.

Operator Description Example Result
and Both must be true (5 > 2 and 3 < 4) True
or At least one true (5 < 2 or 3 < 4) True
not Reverses boolean not (5 == 5) False

Examples in Conditionals:

x = 7

# Using 'and'
if x > 5 and x < 10:
    print("x is between 5 and 10")

is_weekend = True
is_holiday = False

# Using 'or'
if is_weekend or is_holiday:
    print("You can relax today")

logged_in = False

# Using 'not'
if not logged_in:
    print("Please log in")

Nested Conditionals

You can put if statements inside other if statements.

x = 15

if x > 10:
    if x < 20:
        print("x is between 10 and 20")

if...elif...else Statement

Use elif (short for "else if") to check multiple conditions in order.

score = 75

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

Summary

  • Use if, elif, and else to control the flow of your program.
  • Use comparison operators to evaluate values inside conditionals.
  • Use logical operators to combine multiple conditions inside if statements.
  • Nest conditionals for more complex decision trees.

Conditionals make Python programs flexible and interactive.