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Python - Basics

whereisstuffJanuary 29, 2021 No comments

Basics of python language:

To write a c++ program, the following details are needed.

1. Command-line:

It describes what's going on inside a program, so that person looking at the source code does not have a hard time figuring it out.

Types of comments:

(i) Single line comments:

Syntax:

#Statements

Example:

#print function

(ii) Multiline comments:

Syntax:

‘’’Set Statements ‘’’

2.Variables:

A variable is nothing but it allocates the memory space and holds the values.

Syntax fro declaring variables:

variable_name=value;

Example:

a=0 #int data type

s=’ ‘ #String data type

Rules for naming the variables:

The first character must be an alphabet or an underscore (_).
No commas or blank spaces are allowed within a variable name.
No special symbols, an underscore can be used in a variable name.

3. Data types in python:

The most widely used data types in the input function is:

4. Output function:

This function is used to show details on the output screen for user understanding.

Syntax:

print(“Statements”) or

print(‘Statements’)

5. Escape sequence:

This is used to align output on the screen.

Escape sequence	Description	Example	Output
\n	Newline or next line	print(“Hai! \n I am Sabrina.”)	Hai! I am Sabrina.
\t	Horizontal tab(one tab space)	print(“Hai\t Hello”)	Hai hello
\’	Display single-quotes	print(“I don\”t know”)	I don’t know
\”	Display double-quotes	print(“/“Hey/”’)	“Hey”
\\	Print slash	print(“a//b”)	a/b

6. Input function:

This function is used to get value from users.

Syntax:

Variable_name = data_type(input(“ Sentence “))

Example:

a=int (input(“Enter a value : “))

Example program: save example.py

#Write a python program to add of two elements
name=input("Enter your name : ")
a=int(input("Enter a value : "))
b=int(input("Enter b value : "))
c=a+b
print("Add of and b value is : ",c)

Explanation:

name=input("Enter your name : ")

name=str(input("Enter your name : ")) both are same for getting string values.

Output:

Example 2:

If need multiple inputs at one line, then refer to the below program.

Program:

name=str(input("Enter calculation name : "))
a,b=input("Enter a and b value : ").split()
c=int(a)+int(b)
print("Add a of and b value is : ",c)

Explanation:

split() function is used to separate a string from each space.
int(a)+int(b) means, a and b value has string so should be changed into number data type because here performing add operation.

Output:

Example 3:

If displaying value at the sentence like “Add of a and b value is : 10” as “Add of 5 and 5 value is :10”

Program:

name=str(input("Enter calculation name : "))
a,b=input("Enter a and b value : ").split()
c=int(a)+int(b)
print(name+" of "+a+" and "+b+" value is : ",c)

Explanation:

In print function, the + operator is used to join variable of value to a string value.

Output:

Introduction of python programming language:

whereisstuffJanuary 28, 2021 No comments

Python programming language

What is python?

Python is a powerful high level, object oriented, interpreted language.
Proposed by Guido van Rossum in 1989.
It has simple, easy to use syntax and making it the perfect language for someone trying to learn computer programming for the first time.

Wherefrom the python has derived?

In the 1980s, Guido van Rossum was working on the Amoeba distributed OS (ADOS).
He has used ABC language (i.e., interpreted language). This is simple easy to understand syntax in ADOS.
So, he decided to create a language that was extensible (fast).
This is lead to the design new language which was later named “Python”.

Why the name python came?

Guido van Rossum was a fan of a comedy serial from the late seventies.
So, the name python was adopted from the same series “Monty Python’s Flying Circus.

Features of python language:

A simple language that is easier to learn.
Free and open source
Extensible
Large standard library to solve common task.
Object-oriented.

Applications of python:

Web application (Flash, Pyramid, crome, etc)
Scientific and numerical computing (earthpy for earth science, astropy for astronomy, and so on).
Data analytics and machine learning.

Software companies that use python:

Google
Quora
Netflix
Facebook
Instagram
Dropbox etc

Reasons to choose python language:

Python interpreter act as a calculator because python has modes.

1.Shell mode (Python 3.5(32-bit):

Shell mode immediately returns the result of the command for you to enter in the shell.

2.Script mode (IDLE(Python 3.5 32-bit):

The script mode is used to write the script then run and also possible to immediately ran output.
It contains edit options and you can be also, save that py document.

Working with script mode:

Numbers:

String:

A string is a collection of characters or alphabetic and form a sentence or word called a string.
The strings are represented by single or double quotes (“word or sentence“ or
’word or sentence‘).

Note:

Compiler:

It is used to merge all programs into machine code and checking errors.

Interpreter:

It is used to check error line by line and change it line by line machine codes.

If you need more details about the programming language, low-level language, middle-level Language, and high-level language means click the below links to learn.
https://www.whereisstuff.com/2020/09/introductions-of-programming-language.html

Encapsulation in java

whereisstuffDecember 15, 2020 No comments

Encapsulation:

Data encapsulation is used to hide the implementation details from users.
If a data member is private it means it can only be accessed within the same class.
No outside class can access private data member (variable) of other class.

Syntax:

class class_name
{
private data_members;
public methods()
{
}

}

Example program:

class Account {
    private int account_number;
    private int account_balance;

    public void show_Data() {
        account_number=13456;
        account_balance=5000;
        System.out.println("Before deposit of "+"account XXXXX"+account_number+" number of balance :"+account_balance);
    }

    public void deposit(int a) {
        if (a < 0) {
            System.out.println("Given amount is wrong...");
        } else
            account_balance = account_balance + a;
        System.out.println("After deposit of current balance :"+account_balance);
    }
}

class Encapsulation{
    public static void main(String args[])
    {
        Account ac=new Account();
        ac.show_Data();
        ac.deposit(200);
    }

}

Output:

Exception handling in java

whereisstuffDecember 03, 2020 No comments

Exception handling:

Exception in java is an indication of some unusual event.
Usually it indicates the error.
Various keywords used in handling the exception are :
try-A block of source code that is to be monitored for the exception.
catch -The catch block handles the specific type of exception along with the try block.
finally - It specifies the code that must be executed even though exception may or may not occur.
throw - Used to throw specific exception from the program code.
throws - It specifies the exceptions that can be thrown by a particular method.

Syntax:

class class_name
{
try
{
//Exception occures here
}
catch(Exception_type exception_variable)
{
//Exception handling here
}

}

Types of exception:

1) Built-in exceptions:

Before using exception:

public class Divide_By_Zero {
    public static void main(String args[]) {
        int a = 0, b = 0, c = 0;
        a = 5;
        b = 0;
        c = a / b;
        System.out.println(a + " divide by zero of value is : " + c);
    }

}

Output:

Handling above error by using exception:

public class Divide_By_Zero {
    public static void main(String args[])
    {
        int a = 0,b=0,c=0;
        try
        {
            a=5;
            b=0;
            c=a/b;
        }
        catch(ArithmeticException e)
        {
            System.out.println(a+" divide by zero is infinity.");
        }

    }

Output:

Another Example program:

public class Divide_By_Zero {
    public static void main(String args[]) {
        int a[] = new int[3];
        try {
            for (int i = 1; i <= 3; i++) {
                a[i] = i * i;
                System.out.println("Arrsy index"+"\t"+"Added value");
                System.out.println(i+"\t\t"+a[i]);
            }
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Array index is out of bounds.");
        }
    }

}

Output:

2) User-defined exception:

If you need to create user-defined exception, must be constructor method.

Example program:

import java.lang.Exception;
public class user_defined_exception extends Exception {

    public user_defined_exception(String msg) {
        super(msg);
    }
}
class Objects {
    public static void main(String args[]) {
        int age=15;
        try {
            if (age < 21) {
                throw new user_defined_exception("Your age is very less than the condition.");
            }
        } catch (user_defined_exception e) {
            System.out.println("This is exception block.");
            System.out.println(e.getMessage());

        } finally {
            System.out.println("Finally exception block is end.");
        }
    }
}