Returning the Dish (Function Returns)

So far, our functions have acted like recipes that you follow to perform an action, like printing a greeting to the screen. But what if you need a recipe that produces something you can use later?

For example, you don't just "make a sauce"; you make a sauce that you can then add to a pizza. The sauce is the result of the recipe.

In programming, this is called a return value. A function can perform a calculation or a task and then "hand back" the result to the part of the code that called it. This is incredibly powerful because it allows you to build programs from small, productive building blocks.

The return keyword is used to send a value back.

Let's create a function that assembles a sushi roll. It will take an ingredient and a quantity, and it will return a string representing the finished roll.

# This function takes an ingredient and a number,
# then returns a new string.
def make_roll(ingredient, quantity):
  # In Python, you can multiply a string to repeat it.
  sushi = ingredient * quantity
  return sushi

# 1. Call the function and store its result in a variable.
#    The function returns "🍣🍣🍣", which gets saved in 'tuna_roll'.
tuna_roll = make_roll("🍣", 3)

# 2. Call it again to make a different roll.
#    This time, it returns "🥒🥒🥒🥒🥒", saved in 'cucumber_roll'.
cucumber_roll = make_roll("🥒", 5)

# 3. Now we can use our returned values!
print("Here is your tuna roll:", tuna_roll)
print("And your cucumber roll:", cucumber_roll)

# The real power: we can combine the results from our function.
# Let's make a platter!
sushi_platter = tuna_roll + " " + cucumber_roll
print("Enjoy your beautiful platter:", sushi_platter)

// This function takes an ingredient and a number,
// then returns a new string.
function makeRoll(ingredient, quantity) {
  // In JavaScript, you can multiply a string by using .repeat() method.
  let sushi = ingredient.repeat(quantity);
  return sushi;
}

// 1. Call the function and store its result in a variable.
//    The function returns "🍣🍣🍣", which gets saved in 'tunaRoll'.
let tunaRoll = makeRoll("🍣", 3);

// 2. Call it again to make a different roll.
//    This time, it returns "🥒🥒🥒🥒🥒", saved in 'cucumberRoll'.
let cucumberRoll = makeRoll("🥒", 5);

// 3. Now we can use our returned values!
console.log("Here is your tuna roll: " + tunaRoll);
console.log("And your cucumber roll: " + cucumberRoll);

// The real power: we can combine the results from our function.
// Let's make a platter!
let sushiPlatter = tunaRoll + " " + cucumberRoll;
console.log("Enjoy your beautiful platter: " + sushiPlatter);

Notice the key difference: a function with print just displays something on the screen. A function with return gives you a value back that you can store in a variable and use to make further decisions or calculations. This is the primary way that different parts of a program communicate with each other.

Mini-Exercise 💡

1. Define a function called calculate_area that takes two parameters: width and height.
2. Inside the function, calculate the area (width * height) and return the result.
3. Call the function with a width of 10 and a height of 5. Store the returned value in a variable called room_area.
4. Print the room_area.
5. 🔥Bonus: Create another function called calculate_cost that takes the area and a price_per_sq_ft as parameters and returns the total cost. Call this function with your room_area and a price of your choice.