BBP Lesson 8: Functions Extra

:dart: Learning Objectives

By the end of this lesson, you will:

• :emoji: Understand how functions can return values using the return statement
• :emoji: Learn about global variables and how to modify them inside functions
• :emoji: Think of functions as factories that can produce outputs
• :bulb: Create more powerful and flexible programs with advanced function features

:information_source: Remember! A function is a group of predefined codes that will only run when it's called. In this lesson, we're making our functions even more powerful!

Let's Get Started! :rocket:

Return Statements - Functions That Give Back! :emoji:

Have you ever used a vending machine? You put money in (input), and it gives you a snack back (output). Functions can work the same way using return statements!

The Function Factory :emoji:

Imagine a function like a factory in coding:

• :emoji: You provide materials (inputs/arguments)
• :wrench: The factory processes them (function code)
• :package: It gives you a finished product in return (return value)

This is called a return statement, and we can create one with the return block.

Setting Up Return Statements

Step One: Find the return block in your EduBlocks toolbox.

:bulb: Pro Tip!

The return block must always be inside a function - it can't work on its own! Think of it as the factory's delivery door - it needs to be part of the factory building.

Step 2: When using functions with return values, replace the regular function_name block with the special function value block.

Why Use Return Values? :emoji:

When your function returns a value, you can:

• :memo: Place it inside a print() block to display the result
• :link: Use it as input for another function
• :emoji: Store it in a variable for later use

Let's See It In Action!

Input	Output

:bulb: Troubleshooting!

If your function isn't returning anything:

1. Check that the return block is inside your function
2. Make sure you're using the function value block (not the regular function block)
3. Verify that your return block has a value attached to it

Global Variables - Sharing is Caring! :emoji:

Sometimes you need to change a variable that was created outside of your function. This is where global variables come in handy!

The Problem: Variable Scope :emoji:

When you try to change a variable from outside a function, Python gets confused:

Input	Output
	:x:

The Solution: Global Declaration :white_check_mark:

To fix this, you need to tell Python that the variable is global (available everywhere in your program).

Step One: Find the global block in the Statements category.

Step 2: Place the global block at the beginning of your function.

Step 3: Attach your variable name to the global block.

Input	Output
	:white_check_mark:

:information_source: Remember! Think of global variables like announcements on a school PA system - everyone in the school (your program) can hear them! Local variables are like whispers in a classroom - only people in that room (function) can hear them.

:rocket: Optional Challenges for Advanced Coders!

Challenge One: The Calculator Function

Create a function that:

1. Takes two numbers as inputs
2. Adds them together
3. Returns the result
4. Print the result using the function value block

Challenge 2: Global Score Keeper

Create a game score system:

1. Create a global variable called score starting at 0
2. Make a function called add_points that adds 10 to the global score
3. Make another function called double_score that doubles the global score
4. Call both functions and print the final score

Challenge 3: Function Chain

Create three functions where:

1. First function returns a number multiplied by 2
2. Second function takes the result and adds 5
3. Third function takes that result and divides by 3
4. Chain them all together!

:bulb: Connecting to Real Python! :emoji:

In text-based Python, return statements look like this:

python

def add_numbers(a, b):
    return a + b

result = add_numbers(5, 3)
print(result)  # Outputs: 8

And global variables work like this:

python

score = 0

def add_points():
    global score
    score = score + 10

You're Doing Great! :star2:

Fantastic work learning about return statements and global variables! You've just unlocked two powerful features that make your functions much more flexible and useful.

With return statements, your functions can now give back values - just like a vending machine gives you snacks! And with global variables, you can share information across your entire program.

Keep experimenting with these new blocks, and remember: every expert coder started exactly where you are now. You're building amazing skills one block at a time! :tada: