To write our first Python program, we need to download the right interpreter for our PCs.
This book will utilize Python 3. According to the official Python website, Python 2.x is heritage, whereas Python 3.x is the language’s present and future. Furthermore, “Python 3 eliminates many quirks that can unnecessarily trip up beginning programmers” .

However, Python 2 is still frequently used. Python 2 and 3 are around 90% similar. Learning Python 3 will let you grasp Python 2 code with ease. 
To install the Python 3 interpreter, visit https://www.python.org/downloads. The right version should be displayed at the top of the page. To download Python 3, click on the version you want.

To install a different version, scroll down the page and find a list of available versions. Select your desired release version. We’ll be utilizing version 3.4.2 in this book. You will be routed to the download page for the specific version.
At the bottom of the page, you’ll find a table of installers for that version. Select the appropriate installer for your PC. The installer to use relies on two factors:
1. Operating system (Windows, Mac OS, or Linux) 
2. Processor type (32-bit or 64-bit).

If you have a 64-bit Windows machine, you will likely use the “Windows x86-64 MSI installer”. Simply click the link to download it. Don’t worry if you download and execute the wrong installer. You will receive an error notice and the interpreter will not install. To get started, simply download the relevant installer.
After installing the interpreter, you may start coding in Python.

Using Python Shell and IDLE to write our first program.

We’ll use the IDLE program that comes with the Python interpreter to write our code.
To accomplish so, let us first launch the IDLE software. Launch IDLE like any other software. In Windows 8, search for it by typing “IDLE” in the search box.
When you’ve discovered it, click IDLE (the Python GUI) to launch it. You will see the Python Shell as shown below.

The Python Shell allows us to utilize Python in an interactive fashion. This allows us to enter one command at a time. The Shell accepts user commands, executes them, and returns their results. Following this, the Shell awaits the next command.
Try typing the following in the Shell. The commands should be typed on the lines beginning with >>>, while the results are displayed on the following lines.

>> 2+3
5
>>> 3>2
True
>>> print (‘Hello World’)
Hello World

Typing 2+3 sends a command to the Shell to evaluate its value. Thus, the Shell yields 5. By typing 3>2, you are asking the Shell if 3 is greater than 2. The Shell responds “True.” Finally, the print command instructs the Shell to display the line Hello World.

The Python Shell is a useful tool for testing Python commands, particularly for beginners. Exiting and re-entering the Python Shell will erase all previously entered commands. Additionally, the Python Shell cannot be used to generate an actual application. To create a program, type your code in a text file and save it with the.py extension. This file is called a Python script.

To build a Python script, select File > New File from the top menu of our Python Shell. This will launch the text editor where we will create our first program, “Hello World”. Writing the “Hello World” program is a common milestone for beginning programmers. This program will help us become comfortable with the IDLE software.
Enter the following code into the text editor (not the shell).

#Prints the Words “Hello World”
print (“Hello World”)

The line #Prints the Words “Hello World” is highlighted in red, with the word “print” in purple and “Hello World” in green. This is the software’s approach of making our code more readable. The words “print” and “Hello World” have different functions in our application, so they are shown in separate colors. Further details will be provided in following chapters.

The line #Prints the Words “Hello World” (red) is not part of the program. This comment aims to improve code readability for other programmers. The Python interpreter ignores this line. To add comments to our program, insert a # symbol before each line of remarks, as seen below:

#This is a comment
#This is also a comment
#This is yet another comment 

For multiline comments, we can use three single or double quotes, as seen below:

’’’
This is a comment
This is also a comment
This is yet another comment
’’’

Click File > Save As to save your code. Save it using the.py extension.
Done? Voilà! You have successfully written your first Python application.
Finally, click Run > Run Module to start the program (or press F5).
Your Python Shell should display the words “Hello World”.

Please keep in mind that the video was created using Python 2, so some commands may not work properly. To try his scripts, add () to the print statements. Instead of writing ‘Hello World’, use ‘print (‘Hello World’)’. Additionally, modify raw_input() to input(). In Chapter 5, we will explore print() and input() functions.