Learning Python with Raspberry Pi

Chapter 3

Python Basics

IN THE PREVIOUS chapter, we got straight into programming in Python. Hopefully that gave you a good idea of what Python is, but you probably have quite a few questions about how it all worked. In this chapter, we'll aim to answer those questions, and go into detail about exactly how to create your own programs in Python. Then, in later chapters, we'll look at the specific features of Python that help you write particular types of programs for the Raspberry Pi.

Variables, Values, and Types

In the last chapter, we saw that variables can store data we want to use elsewhere. They're one of the most powerful tools programmers can use, and now we'll look at what they actually are. If you've programmed before in a different language, you may notice that Python does things a little differently here.

In the Python interpreter, enter the statement:

>>> score = 0

All this does is tell Python that you want to use score as a new name for the value 0. After this point, whenever Python sees score, it will insert the value 0. To demonstrate this, try entering the following:

>>> print(score)

Remember that Python executes our instructions in order, and you must give score a value before you use it. Otherwise, Python will produce an error.

If you want score to point to some other value, you just assign it a new one, such as:

>>> score = 1

Now, Python will substitute 1 every time it sees the word score (you can verify this by running print(score) again). You can update a ...