Course Content

Python Functions Tutorial

1. What is a Function in Python?

What Is Function?Challenge: Building Functions Arguments Return Value Function Body Built-in Functions

2. Positional and Optional Arguments

Positional Arguments Challenge: Positional Arguments Optional Arguments Challenge: Optional Arguments

3. Arbitrary Arguments

Arbitrary Arguments Arbitrary Keyword Arguments Combination of Positional and Optional Arguments

4. Function Return Value Specification

Single Return Value Multiple Return Values None Return Value Generator Functions Challenge: Traffic lights

5. Recursion and Lambda Functions

Recursion Challenge: Search Engine Lambda Functions Immediately Invoked Lambda Expression Writing Effective and Maintainable Functions

None Return Value

In Python, None is a special object that represents the absence of a value. If we don't specify any return value, None is used by default. It is commonly used to indicate that a function does not return any meaningful result. Let's consider different cases when a None return value can be used:

First Case

When the function does not have a specific result or value to return:


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def greet(name):
    print(f'Hello, {name}!')

result = greet('Alice')
print(result)

In this case, the greet() function simply prints a greeting message without returning a specific value. The default return value is None.

Second Case

When a function is used for its side effects or actions rather than a return value:


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def save_data(data):
    # Save the data to a file or database
    # ...
	print('Data was saved succesfully!')

data = []
result = save_data(data)
print(result)  # output: `None`

In this example, the function save_data() performs actions to save data but does not return a specific result. The return value is None, but the focus is on the side effect of saving the data.

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Section 4. Chapter 3