Because this is going to speak directly into the types of programs that you are going to build out in the future and if you do not understand this topic you are going to find many other concepts very confusing later on. So I highly recommend to pay attention to this guide go through a number of the examples and then if it does not make sense then go through them again until it starts to become a little bit more clear and I think the examples that I put together for this should help to give you some good clarification on the topic and also how it will apply to other tasks in the future.

In looking at the code you can see that I've recreated the full name function here

def full_name(first, last):
  print(f'{first} {last}')

full_name('Kristine', 'Hudgens')

that simply takes in two arguments which is a first name and a last name and then it formats them. Now the key that I want to focus on here is that for the majority of this course we have discussed using the print function so that we could see these values and when it comes to learning introductory topics in Python this is helpful.

However, we are about to graduate into learning how we can actually pass values around in Python programs and the reason why this is so critical is because all the print function allows you to do is to print items in the console and as helpful as that is in a real-world program. The only time that you're ever really going to do this is when you are performing debugging and you want to see what the output of a function is in a real-world program.

You're actually going to return values which means that when you call this full name function here you don't care about it printing this out to the console in a program such as a django or a flask API application. Then all that would do is I would print something out to the logs which is helpful for debugging. Not so helpful if the entire goal is to pass something to say a front-end react application or some type of mobile app and so that is something that is very key to understand which is to decide what it means to have functions return values.

If you have heard me speak before about programming in general then you might have heard me say that you can understand any programming concept as long as you can understand the input and the output of a process. And when we talk about functions it's nice because there is a very clearly defined input and output and it's part of the reason why I absolutely love working with them and I think you will too.

So for this function, our inputs are our arguments here. So first and last these are our inputs now our output right now is technically nothing. So technically the print statement is only printing to this console if we want to work with another part of the program and pass our full name value to it which is a very common process we are going to run into. Then we have to get into what is called the return statement.

So I am going to change this out. I'm going to get rid of the parentheses and so now we have actually changed the behavior even though it may not seem like a big difference. We have changed the behavior of this function. We've actually made it useful now.

So what this means is that whenever we call full_name we are no longer just going to be printing out elements to the console and in fact, in its current state we won't be printing out to the console at all. This is simply going to return a value. And we can test this out by running it and as you can see nothing gets printed out but everything worked.

and so let's see how this can really be used. So instead of simply calling this function, we're going to call it but we are going to set it inside and store the value that gets returned. So this is going to say I want to return this formatted string. We're going to return and store it in this Kristine variable and so now what I can do is I can create another method so I can say def greeting and it expects a full formatted name so I can say greeting name and surname as the argument. And now I can perform a print statement in a real-life application such as a web or mobile application.

def greeting(name):
  print(f')

Then you're going to be performing some tasks such as showing it on the Web site or something like that. So imagine that instead of print right here this is a function that actually renders it onto a Web page. But for right now we do want to actually see this in our terminal so I'm going to keep it here and now I can add another formatted string and say something like hi and then name and then we can end this string. And so now if I come here and I print this out I can call our greeting function and then pass in our Kristine variable. And so it's tested this out to see if it works, and there you can see it has our formatted first and last name and that has been placed directly inside of our greeting function.

And so if that is not clear at all, let's take one last walk through of it. We created a full name function here. It takes a first and a last name as its inputs, as its arguments, it then returns a value it does not print something out to the console it returns a value which is the formatted string which combines the first and last name. From there we called our function and because our function returns a value we were able to store that inside of this Kristine variable and then we're able to use it just like a regular string.

And so hopefully it makes sense that essentially what we've done is if you get rid of this entire full name function call here and simply pass in these values we've pretty much done what we have right here. So if I were to run this you can see that it's identical because essentially what we're doing is when we return this full formatted string we're returning this Kristine Hudgens and we are storing it in this variable and then we can call that from anywhere else in the program.

Now one of the biggest things I wanted to emphasize was the difference between the return and the print statement and so lets call print here instead of calling return and see what happens. Well first we're going to get something kind of weird happening where it prints out the name which's that's expected but then it says Hi None!

The reason why it says hi none is because when we simply print a value out in a function it returns nothing. And so this full name function now it prints something out but it returns None. So Kristine is storing none. And then when we call it from our greeting function that's a reason why it says Hi None!

And so that is not very effective and that's the reason why the return is so important to understand because when it comes to building out entire processes and storing them in functions typically you want to return a value so that you can call that from either another function or just some different part of the program.

So in review that is the key difference between the return and the print statements.

Code

def full_name(first, last):
  return f'{first} {last}'


kristine = full_name('Kristine', 'Hudgens')

def greeting(name):
  print(f'Hi {name}!')


greeting(kristine)