Add/subtract

Write add and subtract functions.

Defining functions (def)

In this lesson we'll introduce the function concept. A function is a reusable block of code. It is defined with def:

def add(x, y):
    return x + y

The def add(x, y) line names the function and its parameters. The indented block is the body. return sends the result out.

You call the function as add(3, 5); the result is 8. We'll cover functions in detail later.

Addition and subtraction

We'll add addition and subtraction functions to the calculator. Each takes two parameters and returns a number:

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

When calling, we pass values to the parameters: add(10, 5) returns 15, subtract(10, 5) returns 5.

Exercise Add addition and subtraction

From the previous lesson a = 10 and b = 5 are already defined. Now add the add(x, y) and subtract(x, y) functions. Then print print(add(a, b)) and print(subtract(a, b)).

Show example solution

def add(x, y):
    return x + y
def subtract(x, y):
    return x - y
print(add(a, b))
print(subtract(a, b))

Test yourself

Complete the function body

def add(x, y):
    ____ x + y

Show answer

def add(x, y):
    return x + y

What does add(3, 4) return for def add(x, y): return x + y?
- 34
- 7
- 3
- It raises an error
Show answer

7 — add(3, 4) returns 3 + 4 = 7.
Match the function concepts

def

Function definition
return

Returning a result
add(3, 5)

Function call
x, y

Parameters

Next lesson: Multiply/divide

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