Python Conditional Statements -- Complete Tutorial

Table of Contents

• What is a Conditional Statement?
• Truthy and Falsy Values
• 1. The if Statement
• 2. The if else Statement
• 3. The elif Statement
• 4. Nested if Statements
• 5. The Ternary Operator (Conditional Expression)
• 6. The match Case Statement (Python 3.10+)
• Short Challenge
• Practice Challenge

What is a Conditional Statement?

A conditional statement is a piece of code that makes a decision. It checks whether a condition is True or False, and runs different code depending on the result.

Think about how many decisions you make every day. "If it's raining, grab an umbrella. Otherwise, wear sunglasses."

Your code can do the same thing. Give it some data, and let it decide what to do next.

is_raining = True

if is_raining:
    print("Take an umbrella!")   # This one runs
else:
    print("Wear sunglasses!")    # This would run if is_raining were False

That's really all there is to it. Check a condition: if it's True, do one thing. If not, do something else.

Truthy and Falsy Values

Here's something people don't tell you at first. You can put almost anything in an if condition — not just True and False. Python treats every value as either "truthy" or "falsy."

These values act like False

Everything else acts like True

# Falsy examples — these if blocks will NEVER run
if 0:
    print("You will never see this")

if "":
    print("This won't print either")

if None:
    print("Nope, not this one")

# Truthy examples — these WILL run
if 42:
    print("Non-zero numbers are truthy")   # This runs

if "hello":
    print("Non-empty strings are truthy")  # This runs

if [1, 2, 3]:
    print("Non-empty lists are truthy")    # This runs

Why should you care?

Experienced developers use this all the time to write cleaner code:

name = input("Enter your name: ")
if name:                     # Same as: if name != ""
    print(f"Hello, {name}!")
else:
    print("You didn't enter a name!")

if name basically means "if name has something in it." An empty string would be falsy, so it falls to else.

1. The if Statement

The if statement runs a block of code only when a given condition is True. If the condition is False, it simply skips that block.

if condition:
    # this code runs only when condition is True

Basic example

age = 18

if age >= 18:
    print("You can vote!")
    print("Go make your voice heard!")

print("This line always runs.")

Things to remember:

• Put a colon : after the condition
• The body must be indented (4 spaces is the standard)
• Everything at the same indentation is part of the same block

With comparison operators

score = 85

if score >= 90:
    print("Grade: A")

if score >= 80:
    print("Grade: B")   # This runs (85 >= 80)

With logical operators (and, or, not)

age = 22
has_ticket = True

if age >= 18 and has_ticket:
    print("Welcome to the show!")   # This runs

if age < 12 or age > 65:
    print("You get a discount!")

if not has_ticket:
    print("Please buy a ticket first")

With membership operators (in, not in)

fruits = ["apple", "banana", "cherry"]

if "banana" in fruits:
    print("We have bananas!")   # This runs

user = "admin"
admins = ["alice", "bob", "charlie"]

if user not in admins:
    print("Access denied")      # This runs

2. The if else Statement

The if else statement gives you two paths — one block of code runs when the condition is True, and a different block runs when the condition is False.

Two paths. Pick one. If the condition is True, the if block runs. If it's False, the else block runs. Never both.

if condition:
    # runs when condition is True
else:
    # runs when condition is False

Basic example

password = "python123"
user_input = input("Enter password: ")

if user_input == password:
    print("Access granted!")
else:
    print("Access denied!")   # Wrong password, this runs

Real-world examples

# Even or odd
number = int(input("Enter a number: "))

if number % 2 == 0:
    print(f"{number} is even")
else:
    print(f"{number} is odd")


# Temperature check
temp = float(input("Enter temperature (C): "))

if temp > 30:
    print("It's hot outside!")
else:
    print("It's pleasant outside.")


# Login check
username = input("Username: ")
if username == "admin":
    print("Welcome, admin!")
else:
    print(f"Welcome, {username}!")

Common mistake: using two ifs when you should use if else

# BAD — both conditions get checked, even though they're opposites
number = 5
if number % 2 == 0:
    print("Even")
if number % 2 != 0:    # This is an extra check. Totally unnecessary.
    print("Odd")

# GOOD — one condition is enough
if number % 2 == 0:
    print("Even")
else:                   # Python already knows it must be odd
    print("Odd")

3. The elif Statement

The elif (short for "else if") statement lets you check multiple conditions one after another. Python runs the block of the first condition that is True, and skips the rest.

Sometimes two paths aren't enough. You have 3, 4, or 10 possibilities. That's where elif comes in.

if condition1:
    # runs if condition1 is True
elif condition2:
    # runs if condition1 is False AND condition2 is True
elif condition3:
    # runs if condition1 and condition2 are False AND condition3 is True
else:
    # runs if ALL conditions above are False

Python checks from top to bottom. The first True condition wins — everything below it gets skipped.

Basic example: Grading system

score = int(input("Enter your score (0-100): "))

if score >= 90:
    print("Grade: A")
elif score >= 80:
    print("Grade: B")
elif score >= 70:
    print("Grade: C")
elif score >= 60:
    print("Grade: D")
else:
    print("Grade: F")

# If score = 85, it prints "Grade: B" (first True match, stops right there)

Another example: Traffic light

light = input("Traffic light color: ").lower()

if light == "green":
    print("Go!")
elif light == "yellow":
    print("Slow down!")
elif light == "red":
    print("Stop!")
else:
    print("Invalid color!")

Multiple conditions per branch with and/or

age = int(input("Enter your age: "))

if age < 0:
    print("Invalid age!")
elif age >= 0 and age <= 12:
    print("Child")
elif age >= 13 and age <= 19:
    print("Teenager")
elif age >= 20 and age <= 64:
    print("Adult")
else:
    print("Senior")

Order matters. A lot.

# WRONG ORDER — the first condition catches everything before the specific one
score = 95

if score >= 60:
    print("Passed")           # This runs, and then the rest is skipped!
elif score >= 90:
    print("Excellent!")       # Never reached!


# CORRECT ORDER — put the most specific condition first
if score >= 90:
    print("Excellent!")       # This runs
elif score >= 60:
    print("Passed")
else:
    print("Failed")

Rule of thumb: Put the most specific (hardest to satisfy) conditions first.

4. Nested if Statements

A nested if is an if statement placed inside another if (or elif/else) block. The inner condition is only checked if the outer condition is True.

Yes, you can put an if statement inside another if statement. That's called nesting.

Use this when you need to check something only after something else has already passed.

Basic example

age = 25
has_license = True

if age >= 18:               # Outer condition
    print("Age check passed")
    
    if has_license:          # Inner condition — checked only if outer is True
        print("You can drive!")
    else:
        print("Get a license first")
else:
    print("Too young to drive")

Real-world: ATM system

# ATM withdrawal
pin_correct = True
balance = 5000
amount = 2000

if pin_correct:
    print("PIN verified.")
    
    if amount <= balance:
        print(f"Withdrawing {amount}...")
        balance -= amount
        print(f"Remaining balance: {balance}")
    else:
        print("Insufficient funds!")
else:
    print("Wrong PIN!")

Nested if inside elif

meal = "dinner"
time_of_day = 20  # 24-hour format

if meal == "breakfast":
    if time_of_day < 12:
        print("Good morning!")
    else:
        print("Late breakfast?")
elif meal == "lunch":
    if 12 <= time_of_day <= 15:
        print("Perfect lunch time!")
    else:
        print("Having lunch late?")
elif meal == "dinner":
    if 18 <= time_of_day <= 22:
        print("Enjoy your dinner!")
    else:
        print("Late dinner!")

When to use nesting vs. and

Sometimes nesting and and can do the same job. Pick whichever is easier to read.

# Both do the same thing. Pick what makes sense.

# Option A: `and` (flat, great for simple cases)
if age >= 18 and has_license:
    print("You can drive!")

# Option B: nesting (better when the inner check has its own else/elif)
if age >= 18:
    if has_license:
        print("You can drive!")
    else:
        print("You need a license first")
else:
    print("You are too young")

Nesting works well when:

• The inner condition has a different else than the outer one
• The inner check needs multiple branches (if/elif/else)
• You want separate error messages for each failure

5. The Ternary Operator (Conditional Expression)

The ternary operator (also called conditional expression) is a shorter way to write an if else in a single line. It returns one value if the condition is True and another if it's False.

Python has a shortcut — the ternary operator. It lets you write an if else in a single line.

value_if_true if condition else value_if_false

Basic example

age = 20
status = "Adult" if age >= 18 else "Minor"
print(status)  # Output: Adult

# Same thing written normally:
if age >= 18:
    status = "Adult"
else:
    status = "Minor"

More examples

# Find the larger number
a, b = 10, 20
max_value = a if a > b else b
print(max_value)  # Output: 20

# Conditional print
number = 7
result = "Even" if number % 2 == 0 else "Odd"
print(result)  # Output: Odd

# Nested ternary (use this carefully — it gets messy fast)
score = 85
grade = "A" if score >= 90 else "B" if score >= 80 else "C" if score >= 70 else "D" if score >= 60 else "F"
print(grade)  # Output: B

# Same thing but more readable with parentheses:
grade = ("A" if score >= 90 else
         "B" if score >= 80 else
         "C" if score >= 70 else
         "D" if score >= 60 else
         "F")

When to use ternary

# GOOD — simple and clear
discount = 0.1 if is_member else 0.0

# BAD — this is a nightmare to read
action = "delete" if user == "admin" and item_exists and not is_locked else "view" if user != "guest" else "login"

# BETTER — complex logic belongs in a normal if else
if user == "admin" and item_exists and not is_locked:
    action = "delete"
elif user != "guest":
    action = "view"
else:
    action = "login"

6. The match Case Statement (Python 3.10+)

Python 3.10 introduced match case. If you've used switch in C or Java, it's similar — but more powerful.

match value:
    case pattern1:
        # do something
    case pattern2:
        # do something else
    case _:
        # default — runs if nothing else matched

The underscore _ is the wildcard — it matches anything. Use it as a default case.

Basic example: Command handler

command = input("Enter command (start/stop/pause): ").lower()

match command:
    case "start":
        print("Starting...")
    case "stop":
        print("Stopping...")
    case "pause":
        print("Pausing...")
    case _:  # default
        print("Unknown command!")

Same thing with if elif:

if command == "start":
    print("Starting...")
elif command == "stop":
    print("Stopping...")
elif command == "pause":
    print("Pausing...")
else:
    print("Unknown command!")

See the difference? match is cleaner and easier to extend.

Matching multiple patterns with |

day = input("Enter a day name: ").lower()

match day:
    case "monday" | "tuesday" | "wednesday" | "thursday" | "friday":
        print("Weekday — time to work!")
    case "saturday" | "sunday":
        print("Weekend — time to relax!")
    case _:
        print("Not a valid day!")

Using if guards inside patterns

You can add an extra condition (called a guard) to a pattern:

value = int(input("Enter a number: "))

match value:
    case n if n > 0:
        print(f"{n} is positive")
    case n if n < 0:
        print(f"{n} is negative")
    case 0:
        print("Zero")
    case _:
        print("Not a number")

Matching against sequences (lists, tuples)

# Match a list
items = ["apple", "banana", "cherry"]

match items:
    case ["apple", "banana", "cherry"]:
        print("Fruit basket!")
    case ["apple", *rest]:
        print(f"Apple with {rest}")
    case _:
        print("Unknown basket")

# Extract values
point = (3, 5)

match point:
    case (0, 0):
        print("Origin")
    case (0, y):
        print(f"On the Y axis at y={y}")
    case (x, 0):
        print(f"On the X axis at x={x}")
    case (x, y):
        print(f"Point at ({x}, {y})")
    case _:
        print("Not a point")

Matching with objects/classes

from dataclasses import dataclass

@dataclass
class Person:
    name: str
    age: int

person = Person("Alice", 30)

match person:
    case Person(name="Alice", age=age):
        print(f"Alice is {age} years old")
    case Person(name=name, age=18):
        print(f"{name} is exactly 18")
    case Person(name=name, age=age):
        print(f"{name} is {age} years old")

When to use match vs if elif