Conditional Statements in Python

Programs become useful when they can make decisions. A decision in Python is based on a condition that becomes True or False.

Conditional statements power real-world logic like:

• Login success or failure
• Discount applied or not
• Access allowed or denied
• Pass or fail results

How Conditions Work

A condition is usually built using comparison operators like >, <, ==, !=. The result is always a boolean value: True or False.

# Conditions return True or False

print(10 > 5)     # True
print(10 == 5)    # False
print(7 != 7)     # False
  

True
False
False

• Python checks each comparison and produces a boolean result.
• Those True/False results are used inside conditional statements.

The if Statement

The if statement runs its block only when the condition is True. If the condition is False, Python skips the block.

# if example: runs only when the condition is True

age = 20

if age >= 18:
    print("Access granted")
  

Access granted

• The condition is age >= 18.
• Because it is True, the message prints.

Indentation is the Block

Python uses indentation to define blocks. Everything indented under if belongs to that block.

# Indentation defines which lines are part of the if block

marks = 75

if marks >= 50:
    print("Pass")          # inside if block
    print("Good job")      # inside if block

print("End of program")    # outside if block
  

Pass
Good job
End of program

• Both indented lines run only when the condition is True.
• The last line runs always because it is not indented.

The if...else Statement

Use else when you want a second path for the False case. This guarantees one of the blocks will run.

# if-else example: one of the two blocks will run

temperature = 25

if temperature > 30:
    print("Weather is Hot")
else:
    print("Weather is Pleasant")
  

Weather is Pleasant

• If the condition is True → if block runs.
• If the condition is False → else block runs.

The if...elif...else Statement

Use elif when you have multiple possible conditions. Python checks conditions from top to bottom and stops at the first True match.

# if-elif-else example: multiple conditions

score = 82

if score >= 90:
    print("Grade: A")
elif score >= 75:
    print("Grade: B")
elif score >= 50:
    print("Grade: C")
else:
    print("Grade: Fail")
  

Grade: B

• Conditions are checked in order.
• Only one block runs in an if-elif-else chain.
• Always keep the strongest condition first (example: 90 before 75).

Logical Operators in Conditions

Real rules often require multiple conditions. Use and, or, and not to combine conditions.

# Logical operators in conditions

age = 22
has_id = True

# and: both must be true
if age >= 18 and has_id:
    print("Entry allowed")

# or: any one true is enough
day = "Sunday"
if day == "Saturday" or day == "Sunday":
    print("Weekend")

# not: reverses True/False
is_blocked = False
if not is_blocked:
    print("User is active")
  

Entry allowed
Weekend
User is active

• and is strict: all conditions must be True.
• or is flexible: one True condition is enough.
• not flips the boolean result.

Nested Conditional Statements

A nested condition is an if inside another if. This is useful when one decision depends on another.

# Nested conditions example

age = 20
has_license = False

if age >= 18:
    if has_license:
        print("You can drive")
    else:
        print("You are eligible, but license is required")
else:
    print("You are underage")
  

You are eligible, but license is required

• Outer condition checks age first.
• Inner condition checks license only if age condition is True.

Chained Comparisons

Python supports a clean style called chained comparisons. It makes range checks very readable.

# Chained comparison example

x = 7

if 1 <= x <= 10:
    print("x is in the range 1 to 10")
else:
    print("x is outside the range")
  

x is in the range 1 to 10

• This is equivalent to: x >= 1 and x <= 10.
• Chaining improves readability.

Truthy and Falsy Values (Important for Real Python)

In Python, some values behave like False even if they are not literally False. These are called falsy values.

Common falsy values:

• 0
• "" (empty string)
• [] (empty list)
• {} (empty dictionary)
• None

# Truthy/falsy examples

name = ""          # empty string (falsy)
items = []         # empty list (falsy)
count = 0          # zero (falsy)

if not name:
    print("Name is missing")

if not items:
    print("No items found")

if not count:
    print("Count is zero")
  

Name is missing
No items found
Count is zero

• This pattern is common in real code validation.
• It avoids long comparisons like if name == "".

Real-World Example: Discount Rule

This example checks total purchase amount and applies a discount only when eligible. This is how e-commerce systems commonly work.

# Discount example using conditions

subtotal = 1499.0
discount_rate = 0.10

# Rule: discount applies only if subtotal is 1000 or more
if subtotal >= 1000:
    discount = subtotal * discount_rate
    final_total = subtotal - discount
    print("Discount Applied:", discount)
    print("Final Total:", final_total)
else:
    print("No discount applied")
    print("Final Total:", subtotal)
  

Discount Applied: 149.9
Final Total: 1349.1

• The condition checks eligibility using >=.
• If eligible, we calculate discount and subtract it.
• Otherwise, subtotal remains the final total.

Common Beginner Mistakes

• Forgetting colon after if/elif/else
• Incorrect indentation (Python is strict)
• Using = instead of == for comparisons
• Wrong ordering in elif ladder (example: checking 50 before 90)

Practice

Quick Quiz

Recap: You learned all major conditional statement types in Python: if, if-else, if-elif-else, nested conditions, logical combinations, chained comparisons, and truthy/falsy behavior.

Next up: Loops in Python — repeating tasks without rewriting code.