4.5 Functions

Functions - blocks of code that are designed to do one specific job.

How to use functions?

def hello_world():
    """Display a simple greeting.

    Args:
        None

    Returns:
        None
    """
    print("Hello World!")

hello_world()

Passing arguments to the function

def hello_name(username):
    """Display a simple greeting with one parameters.

    Args:
        username (str): The username of your user

    Returns:
        None
    """
    print(f"Hello World {username.upper()}!")

hello_name('skillab')

Input - Multiple arguments

A function call would require multiple arguments since a function specification could contain many parameters.

There are many different ways to give arguments to your functions:

• keyword arguments, where each argument consists of a variable name and a value, lists and dictionaries of values

• positional arguments, which must be in the same order as the parameters were written.

# Positional arguments
def hello_name(username, email):
    """Display a simple greeting with 2 parameters.

    Args:
        username (str): The username of your user
        email (str): The email of your user

    Returns:
        None
    """
    print(f"Hello World {username.upper()} with {email.upper()}!")

hello_name('skillab', 'admin@skillab.com')

# Keyword arguments
def hello_name(username, email):
    """Display a simple greeting with 2 parameters.

    Args:
        username (str): The username of your user
        email (str): The email of your user

    Returns:
        None
    """
    print(f"Hello World {username.upper()} with {email.upper()}!")

hello_name(username='skillab', email='admin@skillab.com')
hello_name(email='admin@robotdreams.com', username='robotdreams')

# Best practice is to specify default values and also document them
def hello_name(username='skillab', email='admin@skillab.com'):
    """Display a simple greeting with 2 parameters.

    Args:
        username (str): The username of your user
        email (str): The email of your user

    Returns:
        None
    """
    print(f"Hello World {username.upper()} with {email.upper()}!")

hello_name(email='admin@robotdreams.com', username='robotdreams')
hello_name(username='robotdreams')
hello_name()

Return Values

• A function’s result should not always be displayed on screen.

• A value or combination of values may be returned after processing some data, as an alternative.

• A return value is the value that the function returns.

• A value is taken from a function’s return statement and sent back to the line that called the function.

• Return values let you relocate a lot of your program’s manual tasks into functions, which can reduce the code itself.

def hello_name(username='skillab', email='admin@skillab.com'):
    """Display a simple greeting with 2 parameters.

    Args:
        username (str): The username of your user
        email (str): The email of your user

    Returns:
        string: a string with information about user and mail
    """
    return f"Hello World {username.upper()} with {email.upper()}!"

hello_world = hello_name()