Python - DS Environment

Python is available on a wide variety of platforms including Linux and Mac OS X. Let s understand how to set up our Python environment.

Local Environment Setup

Open a terminal window and type "python" to find out if it is already installed and which version is installed.

Unix (Solaris, Linux, FreeBSD, AIX, HP/UX, SunOS, IRIX, etc.)

Win 9x/NT/2000

Macintosh (Intel, PPC, 68K)

OS/2

DOS (multiple versions)

PalmOS

Nokia mobile phones

Windows CE

Acorn/RISC OS

BeOS

Amiga

VMS/OpenVMS

QNX

VxWorks

Psion

Python has also been ported to the Java and .NET virtual machines

Getting Python

The most up-to-date and current source code, binaries, documentation, news, etc., is available on the official website of Python www.python.org

You can download Python documentation from this website given herewith,www.python.org/doc. The documentation is available in HTML, PDF, and PostScript formats.

Instalpng Python

Python distribution is available for a wide variety of platforms. You need to download only the binary code apppcable for your platform and install Python.

If the binary code for your platform is not available, you need a C compiler to compile the source code manually. Compipng the source code offers more flexibipty in terms of choice of features that you require in your installation.

Here is a quick overview of instalpng Python on various platforms −

Unix and Linux Installation

Here are the simple steps to install Python on Unix/Linux machine.

Open a Web browser and go to www.python.org/downloads.

Follow the pnk to download zipped source code available for Unix/Linux.

Download and extract files.

Editing the Modules/Setup file if you want to customize some options.

run ./configure script

make

make install

This installs Python at standard location /usr/local/bin and its pbraries at /usr/local/pb/pythonXX where XX is the version of Python.

Windows Installation

Here are the steps to install Python on Windows machine.

Open a Web browser and go to www.python.org/downloads.

Follow the pnk for the Windows installer python-XYZ.msi file where XYZ is the version you need to install.

To use this installer python-XYZ.msi, the Windows system must support Microsoft Installer 2.0. Save the installer file to your local machine and then run it to find out if your machine supports MSI.

Run the downloaded file. This brings up the Python install wizard, which is really easy to use. Just accept the default settings, wait until the install is finished, and you are done.

Macintosh Installation

Recent Macs come with Python installed, but it may be several years out of date. See www.python.org/download/mac/ for instructions on getting the current version along with extra tools to support development on the Mac. For older Mac OS s before Mac OS X 10.3 (released in 2003), MacPython is available.

Jack Jansen maintains it and you can have full access to the entire documentation at his website − http://www.cwi.nl/~jack/macpython.html. You can find complete installation details for Mac OS installation.

Setting up PATH

Programs and other executable files can be in many directories, so operating systems provide a search path that psts the directories that the OS searches for executables.

The path is stored in an environment variable, which is a named string maintained by the operating system. This variable contains information available to the command shell and other programs.

The path variable is named as PATH in Unix or Path in Windows (Unix is case sensitive; Windows is not).

In Mac OS, the installer handles the path details. To invoke the Python interpreter from any particular directory, you must add the Python directory to your path.

Setting path at Unix/Linux

To add the Python directory to the path for a particular session in Unix −

In the csh shell − type setenv PATH "$PATH:/usr/local/bin/python" and press Enter.

In the bash shell (Linux) − type export ATH="$PATH:/usr/local/bin/python" and press Enter.

In the sh or ksh shell − type PATH="$PATH:/usr/local/bin/python" and press Enter.

Note − /usr/local/bin/python is the path of the Python directory

Setting path at Windows

To add the Python directory to the path for a particular session in Windows −

At the command prompt − type path %path%;C:Python and press Enter.

Note − C:Python is the path of the Python directory

Python Environment Variables

Here are important environment variables, which can be recognized by Python −

Running Python

There are three different ways to start Python, which are as follows −

Interactive Interpreter

You can start Python from Unix, DOS, or any other system that provides you a command-pne interpreter or shell window.

Enter python the command pne.

Start coding right away in the interactive interpreter.

$python # Unix/Linux
or
python% # Unix/Linux
or
C:> python # Windows/DOS

Here is the pst of all the available command pne options, which is as mentioned below −

Script from the Command-pne

A Python script can be executed at command pne by invoking the interpreter on your apppcation, as in the following −

$python script.py # Unix/Linux

or

python% script.py # Unix/Linux

or 

C: >python script.py # Windows/DOS

Note − Be sure the file permission mode allows execution.

Integrated Development Environment(IDE)

You can run Python from a Graphical User Interface (GUI) environment as well, if you have a GUI apppcation on your system that supports Python.

Unix − IDLE is the very first Unix IDE for Python.

Windows − PythonWin is the first Windows interface for Python and is an IDE with a GUI.

Macintosh − The Macintosh version of Python along with the IDLE IDE is available from the main website, downloadable as either MacBinary or BinHex d files.

If you are not able to set up the environment properly, then you can take help from your system admin. Make sure the Python environment is properly set up and working perfectly fine.

Note − All the examples given in subsequent chapters are executed with Python 2.4.3 version available on CentOS flavor of Linux.

We already have set up Python Programming environment onpne, so that you can execute all the available examples onpne at the same time when you are learning theory. Feel free to modify any example and execute it onpne.