Beginning With Python

You have probablry used computers to do all sorts of useful and interesting things. In each application,
the computer responds in different ways to your input, from the keyboard, mouse or a file. Still the underlying
operations are determined by the design of the program you are given. In this set of tutorials you will learn
to write your own computer programs, so you can give the computer instructions to react in the way you
want.
1.1.1. Low-Level and High-Level Computer Operations. First let us place Python programming
in the context of the computer hardware. At the most fundamental level in the computer there are instructions
built into the hardware. These are very simple instructions, peculiar to the hardware of your particular
type of computer. The instructions are designed to be simple for the hardware to execute, not for humans to
follow. The earliest programming was done with such instructions. If was difficult and error-prone. A major
advance was the development of higher-level languages and translators for them. Higher-level languages
allow computer programmers to write instructions in a format that is easier for humans to understand. For
example
z = x+y
is an instruction in many high-level languages that means something like:
(1) Access the value stored at a location labeled x
(2) Calculate the sum of this value and the value stored at a location labeled y
(3) Store the result in a location labeled z.
No computer understands the high-level instruction directly; it is not in machine language. A special program
must first translate instructions like this one into machine language. This one high-level instruction might be
translated into a sequence of three machine language instructions corresponding to the three step description
above:
0000010010000001
0000000010000010
0000010110000011
Obviously high-level languages were a great advance in clarity!
If you follow a broad introduction to computing, you will learn more about the layers that connect
low-level digital computer circuits to high-level languages.
1.1.2. Why Python. There are many high-level languages. The language you will be learning is
Python. Python is one of the easiest languages to learn and use, while at the same time being very powerful:
It is used by many of the most highly productive professional programmers. A few of the places that use
Python extensively are Google, the New York Stock Exchange, Industrial Light and Magic, .... Also Python
is a free language! If you have your own computer, you can download it from the Internet....
1.1.3. Obtaining Python for Your Computer. If you are not sure whether your computer already
has Python, continue to Section 1.2.2, and give it a try. If it works, you are all set.
If you do need a copy of Python, go to the Downloads page linked to http://www.python.org. Be
careful to choose the version for your operating system and hardware. Chosse a stable version, 3.1 or later.
Do not choose a version 2.X, which is incompatible. (Version 2.6 is described in an older version of this
tutorial.)