Skip to main content

Learning Python Part-8: Python Variables and Python Constants

It is not possible every time for programmer or user to provide input values to be used in program for some operations. This approach is fine when we are working in interactive mode or testing some small programs.

However, in realtime scenarios, most of the times we need to provide and store the values in memory and are used later at the time of executing instructions.

Python Variables:

Variables acts a container that holds data which can be changed later throughout programming. 
For example, 

num = 4

(in above example, “num” is variable that holds value 4 as data and = is an assignment operator )
We can assign multiple variables with different values as below

a = 2
b = 6.6
c = "Python"

Or another simple way, 

a, b, c = 2, 6.6, ”Python"

Also same value can be assigned to multiple variables as below

x = y = z = ”python”

As you may have notice in above examples, value assigned to a variable, can be integer or float or string and others which we will talk about in upcoming posts.

Python Constants:

A constant is a type of variable whose value cannot be changed. In Python, constants are usually declared and assigned on a module. In modules, constants are written in all capital letters and underscores separating the words. 

Module generally means a file containing variables, functions, classes and methods which is imported to another python program. This is done for the purpose of code reusability.

Below is the example of creating a module file and loading this module in another python program.

Create a and add below content to it

PI = 3.14
GRAVITY = 9.8 
Now create a new file and add below code to it. Make sure module ( that we import is in same directory location as that of new file.

import constant


So if you notice here, in this new file we imported previously created module ( And when we execute print for value of PI and GRAVITY from constant module, automatically values associated with these constant are loaded.

Output will be:



Popular posts from this blog

Learning Python Part-6: Python Comments

When it comes to writing a python program, based on the requirements, programs can simple programs of limited number of  lines or it can be really large program which might even span multiple python modules. Now the point here is that, even if we know how to write the program and even we follow correct concepts and syntaxes while writing program, we cannot keep it in our mind forever. We cannot remember each and everything about the program like variables, classes, concepts, functions and so on after some period of time. If the program written by us at some point in time back, once we open it after a period of time, it should not be a situation that we are blank, or guessing why particular code, function and so on. Even it may happen that you are working in a team and program code writing tasks might be shared. So when you put all pieces together written by multiple programmers in your team, you should be able to understand the code. This is where we bring in the concepts of

Learning Python Part-4: Python Keywords

Python has a set of keywords that are reserved words that cannot be used as variable names, function names, or any other identifiers They are used to define the syntax and structure of the Python language. In Python, keywords are case sensitive. There are 33 keywords in Python 3.7.  All the keywords (except True, False and None) are in lowercase. Below is the list of keywords in Python 3.7 I will not be using just syntax to explain these keywords, rather I will use some simple yet enough code examples considering new plus experienced people. For those who are new to python, if you find it difficult  to understand the complete code, just try to see the context and usage of keyword.  False :  This keyword is used to represent a boolean false. If a statement is false, “False” is printed. False in python equals to 0. True: This keyword is used to represent a boolean true. If a statement is true, “True” is printed. True in python equals to 1. None:

Learning Python - Part-5: Python Interfaces

When it comes to working with python, we can always use interactive mode by launching python  or Python3 command as shown in below screenshot.  Image: 1 Once launched we can run all sorts of python operations, however, this approach is not used for development work.  When it comes to writing programs, we generally prefer editors. In fact we can use basic editors like notepad(Windows)/vi editors(Linux). In these editors, once we are done with writing programs, we need to make sure files are stored as .py extension ( Image: 2 ). We simply run python command to execute the programs as shown in below screenshot ( Image: 3 ). Image: 2 Image: 3 Though using normal editors is fine, but when it comes to writing simple, large or complex programs, these basic editors do not offer help or suggestions or correction while writing code. That is where the need of tools that help during programming arises. Below are some of the code editors and IDEs that are widely used.