Module 13 of 15 · Step 1 of 14

Functions

A function gives a reusable group of instructions a name. You can call it whenever you need that work, and it can return a value for the rest of the program.

By the end of this lesson, you can:

Define and call a function
Pass arguments into parameters
Explain return versus print
Use two parameters and a local variable

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Learn · Name a reusable action

Concept 1 of 5

Name a reusable action

def begins a function definition. The body is indented. Defining it does not run it; you must call the function by writing its name followed by parentheses.

Pattern

def say_hi():
    print("Hi")

say_hi()

Code

def say_hi():
    print("Hi")

say_hi()

Output

Hi

Why it works

def stores the action under say_hi.
The indented line belongs to the function.
The call say_hi() makes its body run once.

Common mistake

Not this

def say_hi():
    print("Hi")  # never called

Try this

say_hi()  # call after defining

A definition alone produces no output.