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P A R T I I I
P R O G R A M M I N G W I T H T H E R A S P B E R R Y P I
174
THE RASPBERRY PI gets the first half of its name from a long-standing tradition of using
fruit to name new computing systems—from classic microcomputers like the Acorn, Apricot
and Tangerine to more recognisably modern brands including Apple and BlackBerry—but
the second half comes courtesy of the
Python programming language.
Introducing Python
Flexible and powerful, Python was originally developed in the late 1980s at the National
Research Institute for Mathematics and Computer Science by Guido van Rossum as a succes-
sor to the ABC language. Since its introduction, Python has grown in popularity thanks to
what is seen as a clear and expressive syntax developed with a focus on ensuring that code is
readable.
Python is a high-level language . This means that Python code is written in largely recognisable
English, providing the Pi with commands in a manner that is quick to learn and easy to fol-
low. This is in marked contrast to
low-level languages , like assembler, which are closer to how
the computer “thinks” but almost impossible for a human to follow without experience. The
high-level nature and clear syntax of Python make it a valuable tool for anyone who wants to
learn to program. It is also the language that is recommended by the Raspberry Pi Foundation
for those looking to progress from the simple Scratch (described in Chapter 11, “An
Introduction to Scratch”) to more “hands-on” programming.
Python is published under an open-source licence, and is freely available for Linux, OS X and
Windows computer systems. This cross-platform support means that software written using
Python on the Pi can be used on computers running almost any other operating system as
well—except where the program makes use of Pi-specific hardware such as the GPIO Port.
To learn how Python can be used to address this port, see Chapter 13, “Learning to Hack
Hardware”.
Example 1: Hello World
As you learned in Chapter 11, “An Introduction to Scratch”, the easiest way to learn a new
programming language is to create a project that prints “Hello World!” on the screen. In
Scratch, you just had to drag and drop bricks of prewritten code, but in Python, you need to
write this program entirely by hand.
A Python project is, at heart, nothing more than a text file containing written instructions
for the computer to follow. This file can be created using any text editor. For example, if you
enjoy working at the console or in a terminal window, you can use
nano
; if you prefer a
graphical user interface (GUI), you can use Leafpad. Another alternative is to use an