DEV Community: vishwa v

Python-5(Module

vishwa v — Tue, 04 Aug 2026 15:58:13 +0000

Modularity:
It is the design which used to breaking down larger program into smaller program
In this Reusable sub-parts called modules.

Core concepts of Modularity

Modules
Packages
Import System

Module:
In Python, a module is simply a file that contains Python code — functions, classes, or variables — that you can reuse in other programs. It helps keep your code organized and avoids repetition.

Types of Modules
1.Built-in Modules:
Pre-installed with Python, no extra setup needed

import math
print(math.sqrt(25))   # Output: 5.0

2.User-Defined Modules
Created by developers to organize reusable code.

A module is simply a .py file containing functions, variables, or classes.

Example: calc.py

import calc
print(calc.add(10, 5))   # Output: 15

3.External (Third-Party) Modules
Developed by the community and installed using pip.

Examples:

NumPy → numerical computing

Pandas → data analysis

Requests → HTTP requests

Flask/Django → web development frameworks

import numpy as np
arr = np.array([1, 2, 3])
print(arr)   # Output: [1 2 3]

duck typing language

Duck typing means a language decides what an object is based on what it can do, not what it is declared to be. Python is a classic duck-typed language: if an object has the right methods or attributes, it can be used, regardless of its actual class.

dom-crud

vishwa v — Tue, 04 Aug 2026 14:14:08 +0000

Create (Add new element)

<div id="container"></div>

<script>

  let newPara = document.createElement("p");
  newPara.textContent = "Hello, I am new!";


  document.getElementById("container").appendChild(newPara);
    or
  document.getElementById("list").appendChild(item);
</script>

Adds a new

inside the container.

We use appendChild() or append() in JavaScript to add new elements or content into the DOM. Think of it like placing a new item inside a box — the box is your parent element, and the new item is the child element you’re adding.

Read (Access existing elements)

<p id="msg">Welcome to DOM CRUD</p>

<script>
  let text = document.getElementById("msg").textContent;
  console.log(text); // Output: Welcome to DOM CRUD
</script>

Reads the text of the element.

Update (Modify element content/attributes)

<p id="msg">Old Text</p>

<script>
  let para = document.getElementById("msg");
  para.textContent = "Updated Text";  
  para.style.color = "blue";           
</script>

Updates both text and style.

Delete (Remove element)

<p id="msg">This will be deleted</p>

<script>
  let para = document.getElementById("msg");
  para.remove(); 
</script>

Removes the element completely from the DOM.

Adding blw element

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <h1 id="ha">hi</h1>
  <h1 id="eh">hello</h1>
  <h2 id="One"></h2>

  <button onclick="two()">submit</button>

  <script>
    function two() {
      const element = document.getElementById("One");
      element.innerText = "hello world!";
      element.style.textAlign = "center";

      const parent = document.body;
      const referenceNode = document.getElementById("eh"); 
      parent.insertBefore(element, referenceNode); 
    }
  </script>
</body>
</html>

Python-4

vishwa v — Fri, 31 Jul 2026 15:06:44 +0000

Comparison operator
the operator used to compare the two values(<,>,<=,>=,==)

a = 10
b = 20

print(a == b)   # False (10 is not equal to 20)
print(a != b)   # True  (10 is not equal to 20)
print(a > b)    # False (10 is not greater than 20)
print(a < b)    # True  (10 is less than 20)
print(a >= 10)  # True  (10 is equal to 10)
print(b <= 20)  # True  (20 is equal to 20)

Terinary operator
The ternary operator is just a one-line shortcut for if...else.

num = 5

result = "Even" if num % 2 == 0 else "Odd"
print(result)

Logical operator
A logical operator in Python is used to combine or modify conditions (expressions that evaluate to True or False). They help in decision-making by controlling the flow of the program.

1.and → Returns True if both conditions are true.

2.or → Returns True if at least one condition is true.

3.not → Reverses the result (True becomes False, False becomes True).

x = 10
y = 20

# AND operator
print(x > 5 and y > 15)   # True (both conditions are true)

# OR operator
print(x > 15 or y > 15)   # True (second condition is true)

# NOT operator
print(not(x > 5))         # False (since x > 5 is True, not makes it False)

Run time & Compile time
run time refers to when a program is actively running.
compile time refers to the stage where python checks your code and convert into byte code.

Function overloading
same method name with different number of parameter

example:
add(int a, int b)
add(double a, double b)

Function
Set of instruction with name.
It is a block of code which runs when it is called.
Name must be start with a letter or underscore.

def greet(name):
    return "Hello, " + name

print(greet("vishwa"))

output: Hello, vishwa

Python-3

vishwa v — Thu, 30 Jul 2026 13:54:52 +0000

Conditional statement
It used to control the flow of the execution of the program based on the specific condition.

if statement
It execute whether the given condition is true.

mark=75
if mark>60:
    print("pass")

output:pass

elif statement
Used when you want to check another condition if the first one is false.

marks = 75

if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 50:
    print("Grade C")

output:Grade C

else statement
Runs when none of the above conditions are true.

marks = 30

if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 50:
    print("Grade C")
else:
    print("Fail")

output:Fail

javascript(DOM)

vishwa v — Wed, 29 Jul 2026 15:12:02 +0000

What is Dom
It is an document object model and where it used to represent html allowing javascript to access,change and control the structure and style of the webpage

The DOM is the bridge between HTML and JavaScript that lets you dynamically interact with webpage elements.

Common methods

getElementById() finds an element by its unique ID.

getElementsByClassName() collects all elements with a given class name.

getElementsByTagName() collects all elements with a specific tag.

querySelector() finds the first element that matches a CSS selector.

querySelectorAll() finds all elements that match a CSS selector.

createElement() makes a new HTML element.

appendChild() adds a new child element to a parent.

removeChild() deletes a child element from a parent.

innerHTML changes or gets the HTML content inside an element.

style.property changes the CSS style of an element.

addEventListener() attaches an event (like click or hover) to an element.

Common Methods to Get Elements

let byId = document.getElementById("demo");
let byClass = document.getElementsByClassName("text");
let byTag = document.getElementsByTagName("p");
let byName = document.getElementsByName("username");
let byQuery = document.querySelector(".text");
let byQueryAll = document.querySelectorAll("p");

console.log(byId.innerHTML);       // Hello
console.log(byClass[0].innerHTML); // World

example:change text

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <h1 id="head1">hi</h1>
    <h1 id="head2">hello</h1>
    <h1 id="head3">bye</h1>
    <button onclick="gettext()">change text</button>

    <script>
        function gettext(){
            const element=document.getElementById("head1");
            console.log(element.innerText);
            if(element.innerText=="hi"){
                element.innerText="payilagam";
            }else{
                element.innerText="hi";
            }
        }
    </script>
</body>
</html>

python-2

vishwa v — Tue, 28 Jul 2026 16:25:25 +0000

Keyword in python
In Python, keywords are special reserved words that have predefined meanings and cannot be used as identifiers (like variable names, function names, or class names). They are part of the Python language syntax.

we can see all python keywords using below commands:

import keyword
keyword.kwlist

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

Datatypes
1.Numeric types:

int-postive or negative number
float-Decimal points
complex-real and imaginary part

2.str type

3.sequence type(list,tuple,range)

4.mapping type:
dict-dictonaries that stores data in key-value pairs

5.set types(set,frozen set)

6.boolean type(True or False)

7.None type

Python

vishwa v — Mon, 27 Jul 2026 16:33:15 +0000

Intro
what is programming language:A programming language is a set of formal rules and commands used by humans to write instructions that a computer can understand and execute.

Main Types:
High-Level Languages: Easy for people to read and write (like Python and Java).

Low-Level Languages: Closer to raw machine hardware, making them harder for humans but very fast for machines.

cobal stands for common business-oriented language.it is an english-like computer programming language for business and financial data tasks

Fortron is an formula translation and it is the worlds oldest high-level programming language

Python
It is both a scripting language and a full-fledged, general-purpose programming language

It was created by Guido van Rossum, and released in 1991.

The current version of the python-3.14.6

Why python
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.

diff blw Django and springboot
django is an model view template architecture used in python

springboot is an model view controller architecture used in java

diff blw alpha and beta
Alpha versions: Very early releases where core features are built and tested internally, but code, features, and interfaces may still change or break.

Beta versions: More stable releases where feature sets are locked down, and the focus shifts strictly to fixing bugs and gathering community feedback.

Types of python
cpython-byte code interpreter of python which is written in c.

jpython-java basedd implementation of the python programming language designed to run on the java virtual machine.

python2 vs python3
Python 3 is intentionally not backward-compatible with Python 2 to fix core design flaws, streamline syntax, and provide native Unicode support.

Python 2 reached its official end-of-life on January 1st, 2020, meaning Python 3 is the only version maintained and used for modern development.

Function overloading
Same function name with different number of arguements and multiple functions share the same name but have different parameter structures.

method-5

vishwa v — Thu, 23 Jul 2026 12:29:52 +0000

JavaScript Array keys()
The Array.keys() method returns an Array Iterator object with the keys of an array.

JavaScript Array entries()
The entries() method returns an Array Iterator object with key/value pairs:

[0, "Banana"]
[1, "Orange"]
[2, "Apple"]
[3, "Mango"]

The entries() method does not change the original array.

JavaScript Array with() Method
ES2023 added the Array with() method as a safe way to update elements in an array without altering the original array.

const months = ["Januar", "Februar", "Mar", "April"];
const myMonths = months.with(2, "March")

JavaScript Array Spread (...)
The ... operator expands an array into individual elements.

This can be used join arrays:

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];

const arr3 = [...arr1, ...arr2];

JavaScript Array Rest (...)
The rest operator (...) allows us to destruct an array and collect the leftovers:

Examples

let a, rest;
const arr1 = [1,2,3,4,5,6,7,8];

[a, ...rest] = arr1;

methods-4

vishwa v — Wed, 22 Jul 2026 14:14:19 +0000

JavaScript Array reduceRight()
The reduceRight() method runs a function on each array element to produce a single value.

The reduceRight() works from right-to-left in the array. See also reduce().

const numbers = [45, 4, 9, 16, 25];
let sum = numbers.reduceRight(myFunction);

function myFunction(total, value) {
  return total + value;
}

JavaScript Array every()
The every() method checks if all array values pass a test.

const numbers = [45, 4, 9, 16, 25];
let allOver18 = numbers.every(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

JavaScript Array some()
The some() method checks if some array values pass a test.

const numbers = [45, 4, 9, 16, 25];
let someOver18 = numbers.some(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

JavaScript Array.from()
The from() method can return an array from any variable with a length property.

let text = "ABCDEFG";
Array.from(text);

Js(methods-3)

vishwa v — Tue, 21 Jul 2026 14:06:10 +0000

JavaScript Array flatMap()
The flatMap() method first maps all elements of an array and then creates a new array by flattening the array.

const myArr = [1, 2, 3, 4, 5, 6];
const newArr = myArr.flatMap(x => [x, x * 10]);

JavaScript Array filter()
The filter() method creates a new array with array elements that pass a test.

This example creates a new array from elements with a value larger than 18:

const numbers = [45, 4, 9, 16, 25];
const over18 = numbers.filter(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

JavaScript Array reduce()
The reduce() method runs a function on each array element to produce a single value.

The reduce() method works from left-to-right in the array. See also reduceRight().

const numbers = [45, 4, 9, 16, 25];
let sum = numbers.reduce(myFunction);

function myFunction(total, value, index, array) {
  return total + value;
}

Methods-2

vishwa v — Mon, 20 Jul 2026 15:03:51 +0000

JavaScript Array forEach()

The forEach() method calls a function (a callback function) for each array element.

const numbers = [45, 4, 9, 16, 25];
let txt = "";
numbers.forEach(myFunction);

function myFunction(value, index, array) {
  txt += value + "<br>";
}

JavaScript Array map()
The map() method creates a new array by performing a function on each array element.

The map() method does not execute the function for array elements without values.

const numbers1 = [45, 4, 9, 16, 25];
const numbers2 = numbers1.map(myFunction);

function myFunction(value, index, array) {
  return value * 2;
}

javascript(method-1)

vishwa v — Sun, 19 Jul 2026 13:33:15 +0000

The for...in Loop
The for...in loop iterates over the enumerable properties of an object.

It is typically used for iterating over object keys.

eg:

let person = { name: "Saran", age: 22 };
for (let key in person) {
  console.log(key, ":", person[key]);
}

for...of loop
Used to iterate over arrays, strings, or iterable objects.

let fruits = ["apple", "banana", "cherry"];
for (let fruit of fruits) {
  console.log(fruit);
}