📘 If Statements: Conditional Logic

🎯 Introduction

Welcome to the magical world of if statements! 🎉 In this guide, we’ll explore how to make your Python programs smart enough to make decisions.

You’ll discover how if statements can transform your code from a simple sequence of instructions into an intelligent program that responds differently based on conditions. Whether you’re building a game 🎮, a web app 🌐, or automating tasks 🤖, understanding if statements is essential for writing programs that can think!

By the end of this tutorial, you’ll be writing conditional logic like a pro! Let’s dive in! 🏊‍♂️

📚 Understanding If Statements

🤔 What are If Statements?

If statements are like decision-making crossroads in your code 🛤️. Think of them as a traffic light 🚦 that tells your program which path to take based on certain conditions.

In Python terms, if statements allow your program to execute different blocks of code depending on whether a condition is true or false. This means you can:

• ✨ Make decisions based on user input
• 🚀 React to different situations dynamically
• 🛡️ Validate data before processing

💡 Why Use If Statements?

Here’s why if statements are fundamental to programming:

1. Dynamic Behavior 🎯: Your programs can respond differently to different inputs
2. Error Prevention 🛡️: Check conditions before performing risky operations
3. User Interaction 💬: Create interactive programs that respond to choices
4. Flow Control 🔄: Direct the execution path of your program

Real-world example: Imagine building a weather app 🌤️. With if statements, you can display different messages based on the temperature - “It’s hot! 🌞” or “Bundle up! 🧥”

🔧 Basic Syntax and Usage

📝 Simple If Statement

Let’s start with a friendly example:

# 👋 Hello, if statements!
temperature = 25  # 🌡️ Temperature in Celsius

if temperature > 20:
    print("It's a warm day! ☀️")
    print("Perfect for outdoor activities! 🏃‍♂️")

# 🎨 Checking user age
age = 18

if age >= 18:
    print("Welcome! You can vote! 🗳️")
    print("You're officially an adult! 🎉")

💡 Explanation: Notice how Python uses indentation to define the code block that runs when the condition is true. No curly braces needed!

🎯 If-Else Statements

Add an alternative path with else:

# 🎮 Game access checker
player_level = 15

if player_level >= 20:
    print("🎊 Welcome to the advanced zone!")
    print("⚔️ Prepare for epic battles!")
else:
    print("🌟 Keep playing to reach level 20!")
    print("💪 You've got this!")

# 🛒 Shopping discount
purchase_amount = 75.50

if purchase_amount >= 100:
    discount = purchase_amount * 0.20  # 20% off
    print(f"🎉 You saved ${discount:.2f}!")
else:
    needed = 100 - purchase_amount
    print(f"💡 Add ${needed:.2f} more for 20% discount!")

🔄 If-Elif-Else Chains

Handle multiple conditions:

# 📊 Grade calculator
score = 85

if score >= 90:
    grade = "A"
    emoji = "🌟"
    message = "Outstanding work!"
elif score >= 80:
    grade = "B"
    emoji = "✨"
    message = "Great job!"
elif score >= 70:
    grade = "C"
    emoji = "👍"
    message = "Good effort!"
elif score >= 60:
    grade = "D"
    emoji = "📚"
    message = "Keep studying!"
else:
    grade = "F"
    emoji = "💪"
    message = "Don't give up!"

print(f"{emoji} Your grade: {grade}")
print(f"📝 {message}")

💡 Practical Examples

🛒 Example 1: Smart Shopping Cart

Let’s build a shopping cart with conditional logic:

# 🛍️ Smart shopping cart system
class ShoppingCart:
    def __init__(self):
        self.items = []
        self.total = 0
    
    def add_item(self, name, price, quantity=1):
        # 🛡️ Validate inputs
        if price <= 0:
            print("❌ Invalid price! Price must be positive.")
            return
        
        if quantity <= 0:
            print("❌ Invalid quantity! Must add at least 1 item.")
            return
        
        # ✅ Add item to cart
        item = {
            "name": name,
            "price": price,
            "quantity": quantity,
            "subtotal": price * quantity
        }
        self.items.append(item)
        self.total += item["subtotal"]
        
        print(f"✅ Added {quantity}x {name} to cart! 🛒")
        
        # 🎉 Check for free shipping
        if self.total >= 50:
            print("🚚 Congratulations! You qualify for FREE shipping!")
    
    def apply_discount(self, code):
        # 🎟️ Discount code system
        if code == "SAVE10":
            if self.total >= 30:
                discount = self.total * 0.10
                self.total -= discount
                print(f"✨ Discount applied! You saved ${discount:.2f}")
            else:
                print("💡 Minimum $30 purchase required for this code")
        elif code == "FIRST":
            if len(self.items) == 1:
                discount = 5.00
                self.total -= discount
                print(f"🎊 First-time discount! Saved ${discount:.2f}")
            else:
                print("📝 This code is only for first-time buyers")
        else:
            print("❌ Invalid discount code")
    
    def checkout(self):
        # 💳 Checkout process
        if len(self.items) == 0:
            print("🛒 Your cart is empty!")
            return
        
        print("\n📋 Order Summary:")
        for item in self.items:
            print(f"  • {item['quantity']}x {item['name']} - ${item['subtotal']:.2f}")
        
        print(f"\n💰 Total: ${self.total:.2f}")
        
        # 🏆 Loyalty rewards
        if self.total >= 100:
            points = int(self.total * 10)
            print(f"🌟 You earned {points} loyalty points!")

# 🎮 Let's shop!
cart = ShoppingCart()
cart.add_item("Python Book 📘", 29.99)
cart.add_item("Coffee ☕", 4.99, 3)
cart.add_item("Laptop Stand 💻", 35.00)
cart.apply_discount("SAVE10")
cart.checkout()

🎮 Example 2: Adventure Game Decision System

Create an interactive game with choices:

# 🏰 Text Adventure Game
class AdventureGame:
    def __init__(self, player_name):
        self.player = player_name
        self.health = 100
        self.gold = 50
        self.inventory = ["🗡️ Wooden Sword", "🍞 Bread"]
        self.location = "village"
    
    def show_status(self):
        print(f"\n🎮 {self.player}'s Status:")
        print(f"❤️ Health: {self.health}")
        print(f"💰 Gold: {self.gold}")
        print(f"📍 Location: {self.location}")
        print(f"🎒 Inventory: {', '.join(self.inventory)}")
    
    def make_choice(self, option):
        # 🏰 Village choices
        if self.location == "village":
            if option == 1:  # Visit shop
                self.visit_shop()
            elif option == 2:  # Go to forest
                self.location = "forest"
                print("🌲 You venture into the dark forest...")
                self.forest_encounter()
            elif option == 3:  # Rest at inn
                if self.gold >= 10:
                    self.gold -= 10
                    self.health = min(100, self.health + 30)
                    print("😴 You rest at the inn... (+30 health, -10 gold)")
                else:
                    print("💸 Not enough gold for the inn!")
            else:
                print("❓ Invalid choice!")
    
    def visit_shop(self):
        print("\n🏪 Welcome to the shop!")
        
        # 🛡️ Armor offer
        if "🛡️ Iron Armor" not in self.inventory:
            if self.gold >= 40:
                choice = input("Buy Iron Armor for 40 gold? (y/n): ")
                if choice.lower() == 'y':
                    self.gold -= 40
                    self.inventory.append("🛡️ Iron Armor")
                    print("⚔️ You bought Iron Armor! Defense increased!")
            else:
                print("💸 You need 40 gold for the armor")
        
        # 🧪 Potion offer
        if self.health < 70:
            if self.gold >= 15:
                choice = input("You look hurt! Buy healing potion for 15 gold? (y/n): ")
                if choice.lower() == 'y':
                    self.gold -= 15
                    self.health = min(100, self.health + 50)
                    print("✨ Healed! (+50 health)")
    
    def forest_encounter(self):
        import random
        encounter = random.choice(["monster", "treasure", "merchant"])
        
        if encounter == "monster":
            print("🐺 A wild wolf appears!")
            if "🛡️ Iron Armor" in self.inventory:
                print("🛡️ Your armor protects you! The wolf runs away.")
            else:
                self.health -= 20
                print("💥 The wolf attacks! (-20 health)")
                if self.health <= 0:
                    print("☠️ Game Over!")
        
        elif encounter == "treasure":
            gold_found = random.randint(20, 50)
            self.gold += gold_found
            print(f"💎 You found a treasure chest! (+{gold_found} gold)")
        
        else:  # merchant
            print("🧙‍♂️ A mysterious merchant appears...")
            if self.gold >= 30:
                print("'I have a magic scroll for 30 gold...'")
                # More game logic here

# 🎮 Play the game!
game = AdventureGame("Hero")
game.show_status()
print("\n🏰 You're in the village. What do you do?")
print("1. Visit shop 🏪")
print("2. Go to forest 🌲")
print("3. Rest at inn 🏨")
# game.make_choice(1)  # Uncomment to play!

🚀 Advanced Concepts

🧙‍♂️ Nested If Statements

When you need multiple levels of decisions:

# 🎓 University admission system
def check_admission(gpa, test_score, extracurriculars):
    print("🎓 Checking admission eligibility...")
    
    if gpa >= 3.5:
        if test_score >= 1400:
            if extracurriculars >= 3:
                print("🌟 Congratulations! Full scholarship offered!")
            else:
                print("✨ Accepted with partial scholarship!")
        elif test_score >= 1200:
            print("✅ Accepted! Financial aid available.")
        else:
            print("📝 Waitlisted - strong GPA but improve test scores")
    elif gpa >= 3.0:
        if test_score >= 1500:
            print("✅ Accepted based on exceptional test scores!")
        elif test_score >= 1300 and extracurriculars >= 5:
            print("✅ Accepted - well-rounded application!")
        else:
            print("📋 Application under review")
    else:
        print("📚 Consider improving GPA and reapplying")

# Test the system
check_admission(3.8, 1450, 4)

🏗️ Complex Conditions with Logical Operators

Combine conditions for powerful logic:

# 🏦 Bank loan approval system
def check_loan_eligibility(age, income, credit_score, employment_years):
    # 🎯 Multiple conditions with AND, OR, NOT
    
    if age >= 18 and age <= 65:
        if income >= 30000 and credit_score >= 650:
            if employment_years >= 2:
                print("✅ Loan approved! 🎉")
                
                # 💰 Determine loan amount
                if income >= 100000 and credit_score >= 800:
                    print("💎 Eligible for premium loan up to $500,000")
                elif income >= 50000 or credit_score >= 750:
                    print("✨ Eligible for standard loan up to $200,000")
                else:
                    print("📋 Eligible for basic loan up to $50,000")
            else:
                print("⏰ Need 2+ years employment history")
        elif income >= 25000 and credit_score >= 700 and employment_years >= 5:
            print("✅ Approved for special consideration loan")
        else:
            if credit_score < 650:
                print("📊 Please improve credit score (minimum 650)")
            if income < 30000:
                print("💸 Income requirement not met (minimum $30,000)")
    else:
        if age < 18:
            print("🎂 Must be 18 or older to apply")
        else:
            print("📅 Age limit exceeded for this loan type")

# 🧪 Ternary operator (conditional expression)
status = "Premium" if credit_score >= 800 else "Standard" if credit_score >= 650 else "Basic"
print(f"Customer tier: {status} ⭐")

⚠️ Common Pitfalls and Solutions

😱 Pitfall 1: Assignment vs Comparison

# ❌ Wrong - This assigns instead of comparing!
user_input = 5
if user_input = 5:  # SyntaxError!
    print("Equal to 5")

# ✅ Correct - Use == for comparison
user_input = 5
if user_input == 5:
    print("Equal to 5! ✨")

# 💡 Pro tip: Use 'is' for None, True, False
if user_input is None:
    print("No input provided")

🤯 Pitfall 2: Forgetting Colons and Indentation

# ❌ Missing colon - SyntaxError!
if temperature > 30
    print("It's hot!")

# ❌ Wrong indentation - IndentationError!
if temperature > 30:
print("It's hot!")

# ✅ Correct - colon and proper indentation
if temperature > 30:
    print("It's hot! 🌞")
    print("Stay hydrated! 💧")

🤔 Pitfall 3: Empty If Blocks

# ❌ Empty if block - SyntaxError!
if condition:
    # TODO: add code later

# ✅ Use 'pass' for placeholder
if condition:
    pass  # Placeholder for future code

# ✅ Or better yet, comment out until ready
# if condition:
#     future_code()

🛠️ Best Practices

1. 🎯 Keep Conditions Simple: Break complex conditions into variables

   # Instead of this:
   if age >= 18 and age <= 65 and income > 50000 and credit_score > 700:
       approve_loan()
   
   # Do this:
   is_eligible_age = 18 <= age <= 65
   has_good_income = income > 50000
   has_good_credit = credit_score > 700
   
   if is_eligible_age and has_good_income and has_good_credit:
       approve_loan()

2. 📝 Use Clear Variable Names: Make your conditions self-documenting

3. 🛡️ Handle Edge Cases: Always consider what could go wrong

4. 🎨 Avoid Deep Nesting: Use early returns or elif chains

5. ✨ Leverage Python’s Features: Use in, not in, chained comparisons

🧪 Hands-On Exercise

🎯 Challenge: Build a Password Strength Checker

Create a program that evaluates password strength:

📋 Requirements:

• ✅ Check password length (minimum 8 characters)
• 🔤 Check for uppercase and lowercase letters
• 🔢 Check for numbers
• 🎨 Check for special characters
• 📊 Give a strength score and feedback

🚀 Bonus Points:

• Add specific feedback for improvements
• Check against common passwords
• Suggest strong password examples

💡 Solution

# 🔐 Password Strength Checker
def check_password_strength(password):
    # 📊 Initialize score and feedback
    score = 0
    feedback = []
    strength_emoji = ""
    
    # 📏 Check length
    if len(password) >= 8:
        score += 1
        if len(password) >= 12:
            score += 1
            feedback.append("✅ Great length!")
    else:
        feedback.append("❌ Too short - need at least 8 characters")
    
    # 🔤 Check for uppercase
    if any(char.isupper() for char in password):
        score += 1
    else:
        feedback.append("💡 Add uppercase letters")
    
    # 🔡 Check for lowercase
    if any(char.islower() for char in password):
        score += 1
    else:
        feedback.append("💡 Add lowercase letters")
    
    # 🔢 Check for numbers
    if any(char.isdigit() for char in password):
        score += 1
    else:
        feedback.append("💡 Add numbers")
    
    # 🎨 Check for special characters
    special_chars = "!@#$%^&*()_+-=[]{}|;:,.<>?"
    if any(char in special_chars for char in password):
        score += 1
    else:
        feedback.append("💡 Add special characters (!@#$%^&*)")
    
    # 🚫 Check common passwords
    common_passwords = ["password", "123456", "password123", "admin", "qwerty"]
    if password.lower() in common_passwords:
        score = 0
        feedback = ["⛔ This is a commonly used password - very unsafe!"]
    
    # 📊 Determine strength level
    if score >= 5:
        strength = "Strong"
        strength_emoji = "🔐💪"
        feedback.append("🌟 Excellent password!")
    elif score >= 3:
        strength = "Medium"
        strength_emoji = "🔒"
        feedback.append("👍 Good, but could be stronger")
    else:
        strength = "Weak"
        strength_emoji = "⚠️"
        feedback.append("🛡️ Please strengthen your password")
    
    # 📋 Display results
    print(f"\n🔍 Password Analysis for: {'*' * len(password)}")
    print(f"💪 Strength: {strength} {strength_emoji}")
    print(f"📊 Score: {score}/6")
    print("\n📝 Feedback:")
    for item in feedback:
        print(f"  {item}")
    
    # 💡 Suggest strong password if weak
    if score < 3:
        import random
        suggestions = [
            "Try: MyDog$Name2023!",
            "Try: Coffee#Time@9AM",
            "Try: Sunny*Day&Happy1"
        ]
        print(f"\n💡 Example: {random.choice(suggestions)}")
    
    return score

# 🧪 Test the checker
passwords = [
    "password",
    "Hello123",
    "MyStr0ng!Pass#2023",
    "12345678",
    "Python@Rocks2024!"
]

for pwd in passwords:
    check_password_strength(pwd)
    print("-" * 40)

🎓 Key Takeaways

You’ve mastered if statements! Here’s what you can now do:

• ✅ Write conditional logic to make decisions in your code 💪
• ✅ Use if, elif, and else to handle multiple scenarios 🎯
• ✅ Combine conditions with and, or, not operators 🔧
• ✅ Avoid common mistakes like missing colons or wrong operators 🛡️
• ✅ Build interactive programs that respond to different situations! 🚀

Remember: If statements are the building blocks of intelligent programs. They’re your code’s decision-making superpower! 🦸‍♂️

🤝 Next Steps

Congratulations! 🎉 You’ve conquered if statements!

Here’s what to do next:

1. 💻 Practice with the password checker exercise
2. 🏗️ Add if statements to your existing programs
3. 📚 Move on to our next tutorial: Loops - Making Python Repeat Tasks
4. 🌟 Challenge yourself: Create a text-based game using if statements!

Remember: Every Python expert started with their first if statement. Keep practicing, keep building, and most importantly, have fun! 🚀

Happy coding! 🎉🐍✨