Real Python: The Python return Statement: Usage and Best Practices

The Python return statement is a key component of functions and methods. You can use the return statement to make your functions send Python objects back to the caller code. These objects are known as the function’s return value. You can use them to perform further computation in your programs.

Using the return statement effectively is a core skill if you want to code custom functions that are Pythonic and robust.

In this tutorial, you’ll learn:

• How to use the Python return statement in your functions
• How to return single or multiple values from your functions
• What best practices to observe when using return statements

With this knowledge, you’ll be able to write more readable, maintainable, and concise functions in Python. If you’re totally new to Python functions, then you can check out Defining Your Own Python Function before diving into this tutorial.

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Getting Started With Python Functions#

Most programming languages allow you to assign a name to a code block that performs a concrete computation. These named code blocks can be reused quickly because you can use their name to call them from different places in your code.

Programmers call these named code blocks subroutines, routines, procedures, or functions depending on the language they use. In some languages, there’s a clear difference between a routine or procedure and a function.

Sometimes that difference is so strong that you need to use a specific keyword to define a procedure or subroutine and another keyword to define a function. For example the Visual Basic programming language uses Sub and Function to differentiate between the two.

In general, a procedure is a named code block that performs a set of actions without computing a final value or result. On the other hand, a function is a named code block that performs some actions with the purpose of computing a final value or result, which is then sent back to the caller code. Both procedures and functions can act upon a set of input values, commonly known as arguments.

In Python, these kinds of named code blocks are known as functions because they always send a value back to the caller. The Python documentation defines a function as follows:

A series of statements which returns some value to a caller. It can also be passed zero or more arguments which may be used in the execution of the body. (Source)

Even though the official documentation states that a function “returns some value to the caller,” you’ll soon see that functions can return any Python object to the caller code.

In general, a function takes arguments (if any), performs some operations, and returns a value (or object). The value that a function returns to the caller is generally known as the function’s return value. All Python functions have a return value, either explicit or implicit. You’ll cover the difference between explicit and implicit return values later in this tutorial.

To write a Python function, you need a header that starts with the def keyword, followed by the name of the function, an optional list of comma-separated arguments inside a required pair of parentheses, and a final colon.

The second component of a function is its code block, or body. Python defines code blocks using indentation instead of brackets, begin and end keywords, and so on. So, to define a function in Python you can use the following syntax:

def function_name(arg1, arg2,..., argN):
    # Function's code goes here...
    pass

When you’re coding a Python function, you need to define a header with the def keyword, the name of the function, and a list of arguments in parentheses. Note that the list of arguments is optional, but the parentheses are syntactically required. Then you need to define the function’s code block, which will begin one level of indentation to the right.

In the above example, you use a pass statement. This kind of statement is useful when you need a placeholder statement in your code to make it syntactically correct, but you don’t need to perform any action. pass statements are also known as the null operation because they don’t perform any action.

Note: The full syntax to define functions and their arguments is beyond the scope of this tutorial. For an in-depth resource on this topic, check out Defining Your Own Python Function.

To use a function, you need to call it. A function call consists of the function’s name followed by the function’s arguments in parentheses:

function_name(arg1, arg2, ..., argN)

You’ll need to pass arguments to a function call only if the function requires them. The parentheses, on the other hand, are always required in a function call. If you forget them, then you won’t be calling the function but referencing it as a function object.

To make your functions return a value, you need to use the Python return statement. That’s what you’ll cover from this point on.

Read the full article at https://realpython.com/python-return-statement/ »

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