Quest 14: Functions Part 2 - Side Effects & Procedures

Functions That Do Things Without Returning Values

✨ QUEST 14 | Difficulty: Intermediate | Time: 5 minutes

📊 Complexity Level: Intermediate ⭐⭐

Builds on fundamental concepts from earlier quests. Best for students who have completed Quests 1-6 or have some basic programming experience. This explores different types of functions.

💻 Interactive Options:

📓 Open in JupyterLite - Full Jupyter environment in your browser
▶️ Run code directly below - All code cells on this page are editable and runnable
📥 Download Notebook - For use in local Jupyter or Google Colab

📖 Introduction: Actions vs Rewards

In Quest 6, we learned functions that return values (like spells that give you rewards). But not all functions need to return something. Some just need to do something.

Two types of function outcomes:

With Return 🎁: The function calculates and gives you a result

def calculate_damage(attack, defense):
    return attack - defense  # Returns a value

Without Return 🎭: The function performs an action (side effect)

def announce_victory(winner_name):
    print(f"{winner_name} wins!")  # Doesn't return anything

🎪 Story Time: Imagine a tavern where the Barkeep has two jobs. One job is mixing a potion (returns the potion). Another job is announcing the next quest to the crowd (just tells everyone, doesn’t hand you anything). Both are important functions!

💡 Explanation: Side Effects

A side effect is something a function does besides returning a value: - Print to screen - Modify a list or variable - Write to a file - Display an image - Update game state

🎯 Functions Without Return Values

These functions often have print() statements or modify variables outside the function.

def level_up_player(player_stats):
    """Modifies player_stats in place"""
    player_stats['level'] += 1
    player_stats['experience'] = 0
    print(f"🌟 Level up! Now level {player_stats['level']}")
    # Notice: No 'return' statement!

# The function CHANGED the data but didn't return anything

When return is omitted, the function returns None:

result = level_up_player(player)
print(result)  # Prints: None

🎮 Activity 1: Display Functions

Functions that show information to the player:

🎮 Activity 2: Modifier Functions

Functions that change data:

🎮 Activity 3: Mixed Functions

Often you’ll want both: side effects AND return values:

🧩 Challenge: Build a Logging Function

Write a function that: 1. Takes 3 parameters: message, log_level (like “INFO”, “WARNING”, “ERROR”), and player_name 2. Prints a formatted log message with timestamp-like format 3. Does not return anything 4. Shows different emoji based on log level: - INFO: 📝 - WARNING: ⚠️ - ERROR: 🔴

✅ Solution

🎓 Key Concepts

✨ Functions can do things without returning values (side effects) ✨ Common side effects: printing, modifying lists, updating state ✨ Some functions do BOTH: side effects AND return values ✨ A function without return returns None ✨ Side effect functions are great for “actions” in games!

🚀 What’s Next?

You’ve learned functions that don’t return, and earlier you learned functions that do. Next up: Quest 15: Functions Part 3 - Returning Functions where we dive deeper into writing excellent return-value functions!

--- title: "Quest 14: Functions Part 2 - Side Effects & Procedures" subtitle: "Functions That Do Things Without Returning Values" format: live-html: code-tools: true --- ::: {.quest-badge} ✨ QUEST 14 | Difficulty: Intermediate | Time: 5 minutes ::: ::: {.concept-box} **📊 Complexity Level: Intermediate ⭐⭐** Builds on fundamental concepts from earlier quests. Best for students who have completed Quests 1-6 or have some basic programming experience. This explores different types of functions. ::: ::: {.tip-box} **💻 Interactive Options:** - 📓 **[Open in JupyterLite](../jupyterlite/lab/index.html?path=14-functions-non-returning.ipynb)** - Full Jupyter environment in your browser - ▶️ **Run code directly below** - All code cells on this page are editable and runnable - 📥 **[Download Notebook](../files/lessons/14-functions-non-returning.ipynb)** - For use in local Jupyter or Google Colab ::: ## 📖 Introduction: Actions vs Rewards In Quest 6, we learned functions that **return values** (like spells that give you rewards). But not all functions need to return something. Some just need to **do something**. **Two types of function outcomes:** 1. **With Return** 🎁: The function calculates and gives you a result ```python def calculate_damage(attack, defense): return attack - defense # Returns a value ``` 2. **Without Return** 🎭: The function performs an action (side effect) ```python def announce_victory(winner_name): print(f"{winner_name} wins!") # Doesn't return anything ``` ::: {.story-box} **🎪 Story Time**: Imagine a tavern where the Barkeep has two jobs. One job is mixing a potion (returns the potion). Another job is announcing the next quest to the crowd (just tells everyone, doesn't hand you anything). Both are important functions! ::: ## 💡 Explanation: Side Effects A **side effect** is something a function does *besides* returning a value: - Print to screen - Modify a list or variable - Write to a file - Display an image - Update game state ::: {.concept-box} **🎯 Functions Without Return Values** These functions often have `print()` statements or modify variables **outside** the function. ```python def level_up_player(player_stats): """Modifies player_stats in place""" player_stats['level'] += 1 player_stats['experience'] = 0 print(f"🌟 Level up! Now level {player_stats['level']}") # Notice: No 'return' statement! # The function CHANGED the data but didn't return anything ``` **When return is omitted, the function returns `None`**: ```python result = level_up_player(player) print(result) # Prints: None ``` ::: ## 🎮 Activity 1: Display Functions Functions that show information to the player: ```{pyodide-python} def display_character_sheet(name, level, health, mana): """Display a formatted character sheet""" print("╔════════════════════════════╗") print(f"║ CHARACTER: {name:<19}║") print("╠════════════════════════════╣") print(f"║ Level: {level:<21}║") print(f"║ Health: {health:<20}║") print(f"║ Mana: {mana:<23}║") print("╚════════════════════════════╝") # No return statement! def announce_battle(player_name, enemy_name): """Announce the start of battle""" print(f"\n⚔️ BATTLE START! ⚔️") print(f" {player_name} vs {enemy_name}") print() # Use the functions display_character_sheet("Hero", 5, 80, 40) announce_battle("Hero", "Dark Knight") ``` ## 🎮 Activity 2: Modifier Functions Functions that **change** data: ```{pyodide-python} def add_to_inventory(inventory, item, quantity=1): """Add items to an inventory list""" for _ in range(quantity): inventory.append(item) print(f" ✅ Added {quantity} {item}(s) to inventory") # No return - we modified the list directly! def remove_from_inventory(inventory, item): """Remove an item from inventory""" if item in inventory: inventory.remove(item) print(f" ❌ Removed: {item}") else: print(f" ⚠️ {item} not found!") # Create an inventory my_items = [] print("Starting adventure...") add_to_inventory(my_items, "Sword", 1) add_to_inventory(my_items, "Health Potion", 3) add_to_inventory(my_items, "Rope", 1) print(f"\n📦 Inventory: {my_items}") remove_from_inventory(my_items, "Rope") print(f"📦 Inventory: {my_items}") ``` ## 🎮 Activity 3: Mixed Functions Often you'll want both: side effects AND return values: ```{pyodide-python} def take_damage(current_health, damage): """Take damage and return new health""" new_health = current_health - damage # Side effect: Print what happened print(f" ⚡ DAMAGE: -{damage}") print(f" Current health: {new_health}") # Also return the new value return new_health def heal_player(current_health, heal_amount, max_health=100): """Heal and return new health""" new_health = min(current_health + heal_amount, max_health) # Side effect: Show the healing healed = new_health - current_health if healed > 0: print(f" 💚 HEALED: +{healed}") print(f" Current health: {new_health}") else: print(f" ⚠️ Already at max health!") # Return the result return new_health # Battle scenario health = 100 print("⚔️ In battle!") health = take_damage(health, 25) health = take_damage(health, 15) print() health = heal_player(health, 30) ``` ## 🧩 Challenge: Build a Logging Function Write a function that: 1. Takes 3 parameters: `message`, `log_level` (like "INFO", "WARNING", "ERROR"), and `player_name` 2. Prints a formatted log message with timestamp-like format 3. Does **not** return anything 4. Shows different emoji based on log level: - INFO: 📝 - WARNING: ⚠️ - ERROR: 🔴 ```{pyodide-python} # Challenge: Create a logging function def log_message(message, log_level, player_name): """Log a game message with level and player name""" # YOUR CODE HERE # Hint: Use if/elif to choose emoji based on level # Print something like: "[INFO] Player's Name: message" pass # Test your function: # log_message("Found treasure!", "INFO", "Hero") # log_message("Low health!", "WARNING", "Hero") # log_message("Defeated!", "ERROR", "Hero") ``` ## ✅ Solution ```{pyodide-python} def log_message(message, log_level, player_name): """Log a game message with level and player name""" emoji_map = { "INFO": "📝", "WARNING": "⚠️", "ERROR": "🔴" } emoji = emoji_map.get(log_level, "❓") print(f"[{emoji} {log_level}] {player_name}: {message}") # No return statement! # Test the function log_message("Found treasure!", "INFO", "Hero") log_message("Low health!", "WARNING", "Hero") log_message("Defeated by dragon!", "ERROR", "Hero") ``` ## 🎓 Key Concepts ✨ Functions can do things **without** returning values (side effects) ✨ Common side effects: printing, modifying lists, updating state ✨ Some functions do BOTH: side effects AND return values ✨ A function without `return` returns `None` ✨ Side effect functions are great for "actions" in games! ## 🚀 What's Next? You've learned functions that don't return, and earlier you learned functions that do. Next up: **Quest 15: Functions Part 3 - Returning Functions** where we dive deeper into writing excellent return-value functions!