2.1.1.3 Your first program

The print() function

Look at the line of code below:

print("Hello, World!")

The word print that you can see here is a function name. That doesn't mean that wherever the word appears it is always a function name. The meaning of the word comes from the context in which the word has been used.

You've probably encountered the term function many times before, during math classes. You can probably also list several names of mathematical functions, like sine or log.

Python's functions, however, are more flexible, and can contain more content than their mathematical siblings.

A function (in this context) is a separate part of the computer code able to:

• cause some effect (e.g., send text to the terminal, create a file, draw an image, play a sound, etc.); this is something completely unheard of in the world of mathematics;
• evaluate a value or some values (e.g., the square root of a value or the length of a given text); this is what makes Python's functions the relatives of mathematical concepts.

Moreover, many of Python's functions can do the above two things together.

Where do the functions come from?

• They may come from Python itself; the print function is one of this kind; such a function is an added value received together with Python and its environment (it is built-in); you don't have to do anything special (e.g., ask anyone for anything) if you want to make use of it;
• they may come from one or more of Python's add-ons named modules; some of the modules come with Python, others may require separate installation - whatever the case, they all need to be explicitly connected with your code (we'll show you how to do that soon);
• you can write them yourself, placing as many functions as you want and need inside your program to make it simpler, clearer and more elegant.

The name of the function should be significant (the name of the print function is self-evident).

Of course, if you're going to make use of any already existing function, you have no influence on its name, but when you start writing your own functions, you should consider carefully your choice of names.