Ven's

Learning something new all the time!!!!!!!!!!!!!

[ven-k-blog1]

Python multiprocessing with requests library.

I was trying multiprocessing in Python and I thought requesting urls is where I can use this.

I wrote a small code to request XKCD posts 1821 to 1830 using requests library. It took me 14 seconds on my machine.

I used multiprocessing with requests and the time taken is 4 seconds.

Really good improvement.

Below is what I tried:

https://gist.github.com/84b18d3ffa00e7ac0ae9ed69e6a0468a

[ven-k-blog1]

Using MySQL database with Python

Python can use MySql Database with Python MySQL connector.

MySQL for Python can be installed using following command:

pip install mysqlclient

Below code is a very simple code to connect to a MySQL database based on user inputs.

I created a class inorder and certain datamodel/dunder methods to avoid me forgetting to close the database connection.

In __init__ method, I am initializing certain class variables to use them inside the class.

If we use __enter__ and __exit__ methods in a class, we can create the object of the class with the help of with block.

On entering the with block, the class enters implicitly into __enter__ method and code there gets executed.

On exiting the with block, the class enters implicitly into __exit__ method and work on code there.

In __enter__, I am opening connection and opening a cursor on connection and in __exit__ method closing the cursor and connection.

In the code, I have put docstrings to help understand the code.

Code:

https://gist.github.com/8e381937ef70f9c97540ee103b7b94d7

[ven-k-blog1]

A small introduction to lambdas in Java

Lambdas are introduced in Java 8.

They can be used with functional interfaces.

What is a functional interface ? Interfaces having single abstract method are called Functional Interfaces.

When I said abstract method, you might be thinking why is it explicity said, since from Java 8, static and default methods are also allowed in Java interfaces. So an interface can be created with a combination of abstract, static and default methods.

A functional interface can also be explicitly made one by placing annotation (@FunctionalInterface) above interface and the compiler checks and validates, if interface has more than 1 abstract method, it throws an error.

Examples of Functional Interfaces:

Comparator Runnable etc.

To create a Comparator to use that for sorting, we would've created a class and implemented Comparator interface and overridden compareTo method.

As in below class MyLambdalessExample.java

https://gist.github.com/037212d47d95db09ef8380d553712f03

Person class is a custom Java class:

https://gist.github.com/aa76231bd70fcedec88d3ac8aadbbcc5

With lambdas, this can be reduced to few lines as below.

Lambda structure:

() Open and closed parantheses. If the interface function has parameters they have to be mentioned inside the parantheses. Example: (Person p1, Person p2)

-> The symbol separates lambda header and body.

{ body of lamdba return .... }

A class with Lambda:

https://gist.github.com/21e5cbd12ea7190c19f1b3431b3c87ea

In the example class MyLambda1, in line 29: the lambda can be assigned to a Comparator variable and it can be re-used at other places in class if required. In line 25, I used type Person before parameters p1 and p2, but since we are using this Comparator on a list of type Person, we can get rid of type and instead it can used as in line 29 without type Person.

If the function of the interface has a return type and lambda has more than 1 line, return statement is mandatory.

If the lambda has multiple parameters it should be used with opening and closing braces as in line 38.

For single line lambda bodies, a return keyword is not required. But for lambdas having multiple lines in the body, return is required as we can see in line 38.

[ven-k-blog1]

Creating a simple class in Python

https://gist.github.com/b27912df1ab7b43d3d7cacb414f4a182

[ven-k-blog1]

Simple stack visualization

A simple stack visualization in Codepen.

See the Pen Stack by Venkat K (@venkatk) on CodePen.

[ven-k-blog1]

Quick sort algorithm in Python.

I find the algorithm easy to understand, all we have to do is:

1. Consider a certain element at an index as pivot.

2. Bring elements less than pivot to the left of pivot.

3. Elements greater than pivot will now be on the right of pivot.

4. Repeat the process until a list of size 1 is reached (base case for recursion).

5. Join Left, Pivot, Right.

Below is the code from GitHub Gist:

https://gist.github.com/65ccb83071224cd5afaffe89dcf6ae89

[ven-k-blog1]

Usage of pyperclip Python module to get data from Clipboard

https://gist.github.com/70e7a9ec36813702998dc3b939d90608

[ven-k-blog1]

Dice Roll Simulator using basic Python

The program uses a high value and low value for dice roll.

A dice has numbers 1 to 6.

Dice.

The program generates a random integer between 1 and 6 two times and the user is prompted again if the Dice has to be rolled again.

https://gist.github.com/5dcf837e3e3fcfe73b75c624c3a68df8

[ven-k-blog1]

Basic Exception Handling in Python

https://gist.github.com/3bce73505e7090edbed3790bb6ac3409

[ven-k-blog1]

Custom Wikipedia Search:

https://codepen.io/venkatk/full/YVoBaa/

[ven-k-blog1]

Parallel Scrollbars using JQuery

Codepen: https://codepen.io/venkatk/full/dWNLjJ/

Code from GitHubGist:

https://gist.github.com/da9ad1c143ede0b23227249511c62ddd

[ven-k-blog1]

Data removal from lists in Python

In Python, data can be removed from lists using:

pop () or remove () or del ().

Usages:

https://gist.github.com/78ea7134a640f9249529fdda1f31151b

https://gist.github.com/9c485cf542d05b1a125012b54526d5ab

https://gist.github.com/4788ae906f9d620021c60bb2b4927c23

[ven-k-blog1]

Python Dictionaries

In Python, key value pairs can be accommodated using Dictionary.

A simple example:

https://gist.github.com/d975ec6ce59712a2a6b3eb1397480669

[ven-k-blog1]

Simple way to add code snippets in Tumblr

So cool!

https://gist.github.com/1395926

[ven-k-blog1]

Try resources from java 7

The new format is sort of cool in it’s own way, one wouldn’t have to worry about closing resources.

public class Test {

public static void main (String... args) {

// From java 7. // There's no catch block here. // The new format allows the classes that implement AutoCloseable interface to be // auto closed given they are written in this way. try (BufferedReader br=new BufferedReader(new InputStreamReader(Test.class.getResourceAsStream("FileAtPlace.txt")))) { while (br.readLine()!=null) { System.out.println(br.readLine()); } } // Pre - java 7 try { BufferedReader br=new BufferedReader(new InputStreamReader(Test.class.getResourceAsStream("FileAtPlace.txt"))); while (br.readLine()!=null) { System.out.println(br.readLine()); } } catch (IOException i) { i.printStackTrace(); } } }

About interface AutoCloseable:

https://docs.oracle.com/javase/8/docs/api/java/lang/AutoCloseable.html

[ven-k-blog1]

Starting a Java Thread

1. Class extending Thread class.

public class Class1 extends Thread {

public static void main(String[] args) { Class1 inst1=new Class1();

Class2 inst2=new Class2();

inst1.start();

inst2.start(); } public void run () { for (int i=0;i<100;i++) System.out.println(i); } }

2. Class implementing Runnable interface.

public class Class1 implements Runnable { public static void main(String[] args) { Thread t1 = new Thread (new Class1()); Thread t2 = new Thread (new Class1()); t1.start(); t2.start(); } public void run () { for (int i=0;i<100;i++) System.out.println(i); } }

In both cases run method had to be overridden.

[ven-k-blog1]

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Real time currency converter.