2   Programming Fundamentals and Python

This chapter provides a non-technical overview of Python and will
cover the basic programming knowledge needed for the rest of the
chapters in Part 1. It contains many examples and exercises; there is
no better way to learn to program than to dive in and try these
yourself. You should then feel confident in adapting the example for
your own purposes. Before you know it you will be programming!

2.1   Getting Started

One of the friendly things about Python is that it allows you to type
directly into the interactive interpreter — the program that will be
running your Python programs. You can run the Python interpreter using
a simple graphical interface called the Interactive DeveLopment
Environment (IDLE). On a Mac you can find this under Applications ->
MacPython, and on Windows under All Programs -> Python. Under Unix you
can run Python from the shell by typing python. The interpreter will
print a blurb about your Python version; simply check that you are
running Python 2.4 or greater (here it is 2.5):

There are several things to notice here. First, once the interpreter
has finished calculating the answer and displaying it, the prompt
reappears. This means the Python interpreter is waiting for another
instruction. Second, notice that Python deals with the order of
operations correctly (unlike some older calculators), so the
multiplication 2 * 5 is calculated before it is added to 3.