Python-Modes

Good Morning dear Students

Welcome back to the Computer Science session No. 3

Let us take a quick recap of the previous session before we embark on the next.

What is Python?

Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.

It is used for:

• web development (server-side),
• software development,
• mathematics,
• system scripting.

Why Python?

• Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc).
• Python has a simple syntax similar to the English language.
• Python has syntax that allows developers to write programs with fewer lines than some other programming languages.
• Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick.
• Python can be treated in a procedural way, an object-orientated way or a functional way.

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By the end of this session, you will be able to

• Take a review of the basics of Python
• Understand how to Install Python
• Understand the difference between Python and other programming languages
• understand the two ways of executing Python program
• Write the first Python program and execute the same.

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All of you are expected to copy the contents shared on the blog in your notebooks/registers. 
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Let us begin our session with the discussion-

What can Python do?

• Python can be used on a server to create web applications.
• Python can be used alongside software to create workflows.
• Python can connect to database systems. It can also read and modify files.
• Python can be used to handle big data and perform complex mathematics.
• Python can be used for rapid prototyping, or for production-ready software development.

Good to know

• The most recent major version of Python is Python 3. However, Python 2, although not being updated with anything other than security updates, is still quite popular.
• It is possible to write Python in an Integrated Development Environment, such as Thonny, Pycharm, Netbeans or Eclipse which are particularly useful when managing larger collections of Python files.

Python Syntax compared to other programming languages

• Python was designed for readability, and has some similarities to the English language with influence from mathematics.
• Python uses new lines to complete a command, as opposed to other programming languages which often use semicolons or parentheses.
• Python relies on indentation, using whitespace, to define scope; such as the scope of loops, functions and classes. Other programming languages often use curly-brackets for this purpose.

Installation of Python:

You can download it for free from the following website: https://www.python.org/

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Writing a Python program

Python programs must be

• written in a specific structure.

• Syntax must be correct or the interpreter will generate ERROR messages and will not execute the program

There are two ways of Execution of Python program:-

The Python Command Line 

(Interactive Mode)

To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file. This is made possible because Python can be run as a command line itself.

We need to open Python Shell window and type the commands in front of the Python prompt and Press Enter: Python will immediately give you the result

Let's say hello to the whole world in our following example:

Just type as follows in front of Python Prompt i.e. >>>

C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.

>>> print("Hello, World!")

Which will write "Hello, World!" in the command line:

C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")

Hello, World!

Whenever you are done in the python command line, you can simply type the following to quit the python command line interface:

exit()

The Python IDLE graphic window 

(Script Mode)

Typing and executing one command at time cannot be used for make big program. A programmer is always in need of a text editor in which she/he can easily type the whole code and then execute it after compiling. This is made possible because Python IDLE graphic window.

IDLE is a default editor that comes with Python. After opening it you need to click on 'File' to open a 'New' code editor. This is where we can type Python programs. It allows to insert commands without executing them instantly. 

Let's see the following example:

Please note that in step: 3 File was save and the Window of Step: 4 shows that the file was then named as test.py. In Final Output screen the output of test.py is visible. 

Click on "Try it Yourself" to see the output.

Try it Yourself »

EXERCISE:

(PRACTICAL BASED)

1. All students are requested to install Python by using the link:

           www.python.org

2. Using both SHELL as well as IDLE, try the "Hello, World" Program.

(THEORY BASED)

1. Write the two points which we should keep in mind while writing a Python program?

2. Explain the two ways of executing the Python program?

3. What is the extension of a Python file?