Python: Installation and Executing Python Codes
Versions of Python
Python 1.0 introduced in Jan 1994 (almost gone)
Python 2.0 introduced in October 2000
Python 3.0 introduced in December 2008
We will talk about Python 2 and 3. Both are parallel versions and 3 is not advanced version of 2 and does not provides support for python 2. They are developed as independent programming languages.
Any new version of a software provides support for older version; this is the software rule and is known as backward compatibility. In Python there is no support for backward compatibility. Python-3 does not support Python-2 programmes. For example, code print “Namaste” valid in Python 2 is not valid in Python 3 (for Python 3 code is print (“Namaste”)). Long data type is there in Python 2 but not in Python 3.
Python Organization has ended support for python 2 from January 1, 2020. So, it is recommended to download python 3. Latest version of Python 3 (3.8.2) was released on Feb 25, 2020.
How to install Python
Go to python.org
We are going to download 3.8.2
After installation of python, it is not required to set path manually. Click on Add Python 3.8 to path and path is automatically added.
Customize if you don’t need all functions.
Click on install now.
What is the use of Path Environment variable
Whenever we are using any command like Java or Python immediately windows OS has to execute the corresponding exe file. If we use javac command then windows OS has to execute javac.exe file. From where it is going to execute javac.exe. System will search in the path environment variable. Path:loc1;loc2:loc3… if at any location it found then it is going to execute the exe file.
How many ways we can execute Python Code
Python provides one REPL Tool: Python IDLE. IDLE is an integrated development environment for Python, which has been bundled with the default implementation of the language since 1.5.2b1. It is packaged as an optional part of the Python packaging with many Linux distributions. It is completely written in Python and the Tkinter GUI toolkit. REPL: Read, Evolve, Print, Loop.
1. Print Namaste: Type print (“Namaste”) on Python IDLE .
First it will read the statement then evaluate statement then print it and then again get ready to read the new statement.
2. Run Python Code through Command Promt
From the Command prompt type python or py it will starts the Python shell automatically.
3: Run Python Code through Windows PowerShell:
From the Windows Power Shell type python or py it will starts the Python shell automatically.
Note 1: To Exit From Python Shell, use exit() command.
Note 2: Python shell is used for small coding snippet (just 2 or 3 lines of code). It is not recommended to write larger code on it. If you want to write a program, save your code inside a file, then execute that file.
There are many options in Python IDLE like:
File - Create new file, open existing file and many more
Edit - Undo, Redo , Copy, Paste
Shell - vie last start, restart shell, next and previous history
Debug - go to debugger
Options - configure IDLE
Windows - go to Python 3.8.2 shell
Help - About IDLE, Turtle graphics Examples
Read some int values from the keyboard (dynamic input) print those many number of times message.
We are going to write this program in a file and then execute it.
Open Python IDLE
Click on File
Then Click on new File
Write the code
n = int(input("Enter some number"))
// enter a number and type casting in int
for i in range(n): // for loop
print("Hello how are you")
Save the file with any name but extension must be .py. I have saved it with name Exaple.py.
How to execute the file:
Click on run.
A new window will open. Provide your input for example 5.
Then it will print the message 5 times
Programme:3 Read two numbers from the keyboard (dynamic input) and print their Addition, Subtraction and Multiplication
Write This program in a file and save it Example2.py (you can save with any name)
x=int(input("Enter First number"))
y=int(input("Enter Second number"))
Run Example1.py file with cmd:
Change the path
Type the name of program (Example.py)
In the previous examples we have used notepad.
Now we are going to used EditPlus editor (5.3 Evaluation Version)
EditPlus provides 30 days trail.
For installation Go to editplus.com
Click on accept
Specify a path and then click on Start Copy
You will get a message click on OK.
Click on Trial
Various File Type Supported by EditPlus
Why EditPlus is required when notepad is there?
Debugging is easy in EditPlus.
Keywords in blue color and Functions in grey color.
More readable and easier to write codes.
You can also use Notepad++ for the same functionalities.
When we will work to develop big application then we will use IDEs (Integrated Development Environment) in which 70% of the code is generated automatically. There are many IDEs like
Note: When basic concepts are clear then we will use IDEs, till then we will work with Editors.
For any Query/Suggestion, do let us know in the comment section.