Returning None Explicitly

00:00 Now that you know the syntax of writing return statements in Python, let’s take a look at some best practices when using it. First, we’ll look at returning None explicitly. As you’ve seen, Python will return a value of None in several situations, but there might be occasions to actually write out a return None statement.

00:19 There are basically three ways to cause a value of None to be returned from a function: if the function doesn’t have a return statement at all, if you have a return statement with no return value, or you can explicitly return None.

00:35 Let’s verify that all three of these cases actually do return a value of None. So, here’s a function with no return statement.

00:47 Remember, we use the keyword pass to indicate an empty function body. If we just call this function,

00:57 we don’t see anything. Remember, the interpreter won’t show a return value of None. You actually have to print the result of a function call to see that it does indeed return None.

01:11 Next, we’ll look at having just a bare return statement,

01:17 so we’ll have return but no return value. If we print the result of its function call, we get None. And lastly, we can explicitly return None.

01:36 We return None, and print the result of its function call.

01:46 We see we get None again. So all of these return None. So, what are some factors to consider when you need to decide which to use?

01:56 If your function performs actions but doesn’t have a clear and useful return value, then you can omit the return statement, although you could use a bare return statement just to make clear your intention of returning from the function.

02:09 If your function has multiple branches with return statements and returning None would be a reasonable value for one or more of those branches, then you should consider the explicit use of return None instead of relying on Python’s default behavior. A word of caution: many Python programmers come from other programming languages, so not having a return statement at all for a function might be confusing for those who are used to referring to such subprograms as procedures.

02:38 This might be an issue to consider in thinking about the long-term maintainability of your project. Next, we’ll look at two other best practices involving remembering the return value and avoiding complex expressions.