Python - Environment Setup

The first step in the journey of learning Python is to install it on your machine. Today, most computer machines, especially those running Linux OS, have Python pre-installed. However, it may not be the latest version.

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.

• 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.

Local Environment Setup

Open a terminal window and type python to find out if it is already installed and which version is installed. If Python is already installed, then you will get a message similar to the following:

$ python
Python 3.11.2 (main, Feb 8 2023, 14:49:24) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>>

Downloading Python

The most up-to-date and current source code, binaries, documentation, news, etc., are available on the official Python website:

https://www.python.org/

You can download Python documentation from:

https://www.python.org/doc/

The documentation is available in HTML, PDF, and PostScript formats.

Installing Python

Python distribution is available for a wide variety of platforms. You need to download only the binary code applicable 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. Compiling the source code offers more flexibility in terms of the choice of features that you require in your installation.

Here is a quick overview of installing Python on various platforms.

Install Python on Ubuntu Linux

To check whether Python is already installed, open the Linux terminal and enter the following command:

$ python3.11 --version

In Ubuntu Linux, the easiest way to install Python is to use the APT (Advanced Packaging Tool). It is always recommended to update the list of packages in all the configured repositories.

$ sudo apt update

Even after the update, the latest version of Python may not be available for installation, depending upon the version of Ubuntu you are using. To overcome this, add the deadsnakes repository.

$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:deadsnakes/ppa

Update the package list again.

$ sudo apt update

To install the latest Python 3.11 version, enter the following command in the terminal:

$ sudo apt-get install python3.11

Check whether it has been properly installed.

$ python3

Python 3.11.2 (main, Feb 8 2023, 14:49:24) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> print ("Hello World")
Hello World

>>>

Install Python on Other Linux Systems

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

1. Open a web browser and go to:
2. https://www.python.org/downloads/
3. Follow the link to download zipped source code available for Unix/Linux.
4. Download and extract files.
5. Edit the Modules/Setup file if you want to customize some options.
6. Now issue the following commands:

$ ./configure
$ make
$ make install

This installs Python at the standard location /usr/local/bin and its libraries at:

/usr/local/lib/pythonXX

where XX is the version of Python.

Using Yum Command

Red Hat Enterprise Linux (RHEL 8) does not install Python 3 by default. We usually use the yum command on CentOS and other related variants. The procedure for installing Python 3 on RHEL 8 is as follows:

$ sudo yum install python3

Install Python on Windows

It should be noted that Python version 3.10 onwards cannot be installed on Windows 7 or earlier operating systems.

The recommended way to install Python is to use the official installer. A link to the latest stable version is given on the home page itself. It is also found at:

https://www.python.org/downloads/windows/

You can find embeddable packages and installers for both 32-bit and 64-bit architectures.

Let us download the 64-bit Windows installer:

https://www.python.org/ftp/python/3.11.2/python-3.11.2-amd64.exe

Double-click on the file where it has been downloaded to start the installation.

Although you can proceed directly by clicking the Install Now button, it is advised to choose the installation folder with a relatively shorter path and tick the second checkbox to update the PATH variable.

Accept the defaults for the remaining steps in the installation wizard to complete the installation.

Open the Windows Command Prompt terminal and run Python to check the success of the installation.

C:\Users\Acer>python

Python 3.11.2 (tags/v3.11.2:878ead1, Feb 7 2023, 16:38:35)
[MSC v.1934 64 bit (AMD64)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>>

Python's standard library has an executable module called IDLE, short for Integrated Development and Learning Environment. Find it from the Windows Start Menu and launch it.

IDLE contains the Python shell (interactive interpreter) and a customizable multi-window text editor with features such as syntax highlighting, smart indenting, auto-completion, etc. It is cross-platform, so it works the same on Windows, macOS, and Linux. It also includes a debugger with provisions for setting breakpoints, stepping through code, and viewing global and local namespaces.

Steps to Install Python on Windows

1. Open a web browser and go to:
2. https://www.python.org/downloads/
3. Follow the link for the Windows installer python-XYZ.msi file where XYZ is the version you need to install.
4. To use this installer, the Windows system must support Microsoft Installer 2.0. Save the installer file to your local machine and run it to verify MSI support.
5. Run the downloaded file.
6. The Python installation wizard will appear. Accept the default settings, wait for the installation to finish, and you are done.

Macintosh Installation

Recent Macs come with Python installed, but it may be several years out of date.

See:

http://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 versions before Mac OS X 10.3 (released in 2003), MacPython is available.

Jack Jansen maintains it, and full documentation is available at:

https://homepages.cwi.nl/~jack/macpython/index.html

You can find complete installation details for Mac OS installation there.

Setting Up PATH

Programs and other executable files can reside in many directories, so operating systems provide a search path that lists the directories 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:

• PATH in Unix/Linux
• Path in Windows

(Unix is case-sensitive; Windows is not.)

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

Setting PATH on Unix/LinuxTo add the Python directory to the path for a particular session in Unix:

In the csh shell

setenv PATH "$PATH:/usr/local/bin/python"

In the bash shell (Linux)

export PATH="$PATH:/usr/local/bin/python"

In the sh or ksh shell

PATH="$PATH:/usr/local/bin/python"

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

Setting PATH on WindowsTo add the Python directory to the path for a particular session in Windows:

path %path%;C:\Python

Note: C:\Python is the path of the Python directory.

Python Environment Variables

Here are important environment variables that can be recognized by Python.

PYTHONPATH

PYTHONPATH has a role similar to the PATH environment variable. It tells the Python interpreter where to locate module files that are imported into a program. This variable should include the Python source library directory as well as any directories containing Python source code. In many cases, PYTHONPATH is automatically configured by the Python installer.

PYTHONSTARTUP

PYTHONSTARTUP contains the path to an initialization file that holds Python source code. This file is executed automatically every time the Python interpreter starts. On Unix systems, it is commonly named .pythonrc.py and usually contains commands that load utilities, customize the Python environment, or modify the PYTHONPATH variable.

PYTHONCASEOK

PYTHONCASEOK is used on Windows systems to instruct Python to perform case-insensitive matching when processing import statements. When this variable is set to any value, Python will search for the first matching module regardless of letter case, making imports less strict with respect to capitalization.

PYTHONHOME

PYTHONHOME provides an alternative module search path for the Python interpreter. It is often used together with the PYTHONSTARTUP or PYTHONPATH environment variables to simplify the management of Python installations and make it easier to switch between different module libraries and environments.

Running Python

There are three different ways to start Python.

Interactive InterpreterYou can start Python from Unix, DOS, or any other system that provides a command-line interpreter or shell window.

Enter python at the command line.

Start coding right away in the interactive interpreter.

$ python        # Unix/Linux

or

python%         # Unix/Linux

or

C:\> python     # Windows/DOS

Command-Line Options

-d Option

The -d option is used to provide debug output. It enables additional debugging information from the Python interpreter, which can be useful for developers when diagnosing issues or understanding how Python processes code internally.

-O Option

The -O option tells Python to generate optimized bytecode. When this option is used, Python performs certain optimizations and creates optimized bytecode files, which traditionally resulted in .pyo files. This option can help improve execution efficiency in some cases.

-S Option

The -S option prevents Python from automatically running the import site command during startup. As a result, Python does not search for additional site-specific paths and configurations, which can reduce startup time and provide a more controlled execution environment.

-v Option

The -v option enables verbose output. It provides detailed information about module imports and other startup activities, allowing developers to trace how Python locates and loads modules during program execution.

-X Option

The -X option was originally used to disable class-based built-in exceptions and rely on string exceptions instead. However, this option became obsolete starting with Python version 1.6 and is no longer commonly used in modern Python environments.

-c cmd Option

The -c cmd option allows you to execute Python code directly from the command line without creating a script file. The code is provided as a string immediately after the -c option and is executed by the Python interpreter.

file Option

The file option is used to run a Python script stored in a file. By specifying the filename after the Python command, the interpreter reads and executes the script contained in that file. This is the most common way to run Python programs.

Script from the Command LineA Python script can be executed at the command line by invoking the interpreter on your application.

$ 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 application 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 and can be downloaded 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 administrator. Make sure the Python environment is properly set up and working perfectly fine.

We have provided a Python Online Compiler/Interpreter that helps you edit and execute code directly from your browser. Try clicking the Run button to execute the following Python code and print the conventional "Hello, World!" message.

The code box below allows you to change the code. Try modifying the value inside print() and run it again to verify the result.

# This is my first Python program.
# This will print 'Hello, World!' as the output

print("Hello, World!")