Varun Pant

Cloud composer orchestration via cloud build

Mon, 25 May 2020 00:00:00 +0000

Cloud composer orchestration via cloud build

Google cloud composer is a managed apache airflow service that helps create, schedule, monitor and manage workflows.Cloud Composer automation helps you create Airflow environments quickly and use Airflow-native tools, such as the powerful Airflow web interface and command line tools, so you can focus on your workflows and not your infrastructure.

In this article I will descibe how an engineering team can manage, develop and publish DAGS after running a full CI/CD build pipeline using google cloud build .

Simple Forecasting

Thu, 26 Dec 2019 00:00:00 +0000

Timeseries financial forecasting

Recently , I have been looking into various ways to forecast a time series dataset. This is an old pursuit in the field of statistics and there are many well known ways to achieve this.

In this post I will demonstrate a very basic (Naive) approach of forecasting a quarterly dataset of sales figure, by using previous 4 years (16 quarters) and forecasting/predicting the next 1 year of sales aggregate.

how to install the latest python 3 on mac

Mon, 09 Sep 2019 00:00:00 +0000

Here is a quick guide on installing Python3 on a mac

Installation

brew update
brew upgrade
sudo mkdir -p /usr/local/Frameworks
sudo chown -R $(whoami) /usr/local/*
brew install python3
brew link python3
brew doctor

Aliasing

 echo "alias python=/usr/local/bin/python3.7" >> ~/.zshrc

echo "alias python=/usr/local/bin/python3.7" >> ~/.bashrc

You could probably have just done this as well

alias python='python3'
alias pip='pip3'

I hope this is useful

how to play apple music on alexa in uk

Wed, 10 Apr 2019 00:00:00 +0000

You can now use Alexa to play Apple Music on Amazon Echo speakers.

It’s just available for Echo devices and now customers in UK can also connect their apple music account with Alexa.

Open the Alexa app then sign into your Amazon account and make sure that your Echo device is connected.
Open Menu (top left icon), then select settings.
Select Music.
Select “Link New Service”
Tap, Apple music Icon

download file using webdriver firefox and python selenium

Sun, 24 Feb 2019 00:00:00 +0000

Selenium is one of my favourite tool for automation.

In this post, I will demonstrate some basic code to download a file from a website in a headless mode , and also provide a docker file to make things simpler.

Python Code

Here is some basic code which will make an attempt to download a **7zip exe. **

from pyvirtualdisplay import Display
from selenium import webdriver
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected\_conditions as EC
from selenium.webdriver.common.by import By
import os
import time

print("******************************** STARTING ********************************")

display = Display(visible=0, size=(1024, 768))
display.start()

# To prevent download dialog
profile = webdriver.FirefoxProfile()
profile.set\_preference('browser.download.folderList', 2) # custom location
profile.set\_preference('browser.download.manager.showWhenStarting', False)
profile.set\_preference('browser.download.dir', '/srv/download')
profile.set\_preference("browser.download.manager.alertOnEXEOpen", False)
profile.set\_preference("browser.download.manager.closeWhenDone", False)
profile.set\_preference("browser.download.manager.focusWhenStarting", False)
#application/octet-stream,application/vnd.ms-excel 
profile.set\_preference('browser.helperApps.neverAsk.saveToDisk', 'application/x-msdownload,application/octet-stream')
try:
    browser = webdriver.Firefox(profile)
    browser.get('https://www.7-zip.org/')
    download\_button = WebDriverWait(browser, 20).until(EC.element\_to\_be\_clickable((By.CSS\_SELECTOR, 'td.Item a')))
    download\_button.click()
    print("clicked...")
    time.sleep(10) 
    print (os.listdir("/srv/download"))
except Exception as ex:
    print(ex)
 
browser.close()
display.stop()


print("******************************** FINITO ********************************")

The code is fairly simple , we need

About

Fri, 25 Jan 2019 00:00:00 +0000

My name is Varun, I occasionally write about tech stuff that I find interesting.

I can also be found at:

Stack-overflow

Github

Showcase

Fri, 18 Jan 2019 00:00:00 +0000

web crawling or scraping using scrapy in python

Sun, 02 Dec 2018 00:00:00 +0000

Scrapy is a very popular web scraping/crawling framework, I have been using it for quite some time now.

In this post, I will demonstrate creating a very basic web crawler.

Install Scrapy

Installation is via pip pip install scrapy

Minimalistic Code

A very simple scraper is created like this

To Run , simply type scrapy runspider scraper.py

Running, above code will output something like below

integration testing with apache beam using pubsub and bigtable emulators and direct runner

Fri, 03 Aug 2018 00:00:00 +0000

Summary

Recently I have been looking into ways to test my Apache Beam pipelines at work. Most common use cases of Beam generally involves either batch reading data from GCS and writing to analytical platforms such as Big Query or stream reading data from Pubsub and writing to perhaps Bigtable.

A pipelines consists of transforms and its generally easy to test them in isolation as a independent unit test per stage, however I am personally a big fan of “end-to-end” testing or “Integration testing” and this is where things can sometimes get tricky.

gdal 2 on mac with homebrew

Tue, 13 Feb 2018 00:00:00 +0000

GDAL is one of the most frequently used utility in my toolkit. I am writing this post to make it easier for others to install it from scratch on their macs.

Setting up GDAL

The traditional way has always been to visit the dear old kyngchaos.com, and install “GDAL Complete” Framework vi deb installer. Do make sure that GDAL Framework is in your path otherwise something like this always helps

how to print bar chart in chrome browser console

Mon, 05 Feb 2018 00:00:00 +0000

This post doesn’t really have anything valuable to contribute, just some cool console trick.

Have you ever wanted to plot out a chart, very quickly ? Did you ever had an urge to visualise a bunch of numbers without having to use a charting api or copy pasting the data in a spreadsheet ? If you did then you might even learn something today :)

Here is a simple , yet neat way to plot out bunch of numbers in chrome console as a** horizontal bar chart.**

how to make https requests with python httplib2 ssl

Fri, 02 Feb 2018 00:00:00 +0000

Here are few snippets to make secure http requests using various python libraries.

httplib2

import httplib2

link = "https://example.com
h = httplib2.Http(".cache")
r, content = h.request(link, "GET")

another exmaple


import httplib2

h = httplib2.Http(".cache")
h.add_credentials('user', 'pass')
r, content = h.request("https://api.github.com", "GET")

print r['status']
print r['content-type']

Urllib2

Here is a simmilar example using urlib2 for comparison and lines of code.


import urllib2

gh_url = 'https://example.com'

auth_handler = urllib2.HTTPBasicAuthHandler()
auth_handler.add_password(None, gh_url, 'user', 'password')

opener = urllib2.build_opener(auth_handler)
urllib2.install_opener(opener)
handler = urllib2.urlopen(gh_url)

print handler.getcode()
print handler.headers.getheader('content-type')

Requests

The easiest, has always been requests.

how to read json from web http request of url via python urllib

Tue, 30 Jan 2018 00:00:00 +0000

I generally am looking for a quick snippet to issue an http request using urllib2 lib.

Here is a quick snippet to do so


import urllib2
import json
from pprint import pprint
req = urllib2.Request(url)
opener = urllib2.build\_opener()
f = opener.open(req)
#data varibale recieves the parsed json
data = json.loads(f.read())
print len(data)
for r in data:
pprint(r)
print "-"*50

Hope this helps

minimum insertions to form a palindrome

Sun, 15 Oct 2017 00:00:00 +0000

Brute-force approach

Here I present a few approaches to deduce “minimum insertions” required to convert a string into a palindrome.

The basic brute force approach is quite simple, given a string with length L, start comparing, the first character from left and the last character while scanning inwards.

Here is a basic test for a palindrome.

 L = len(s)
 for i in range(L):
 if s[i] != s[L - i - 1]:
 return False,i,L-i -1
 return True,0,0

The above code returns True if the string is a palindrome or returns False with mismatching indices.

Inverse weighted distance interpolation in golang

Thu, 07 Sep 2017 00:00:00 +0000

Inverse distance weighting (IDW) is a type of deterministic method for multivariate interpolation with a known scattered set of points. The assigned values to unknown points are calculated with a weighted average of the values available at the known points.

This technique, explicitly makes the assumption that things that are close to one another are more alike than those that are farther apart. To predict a value for any unmeasured location, IDW uses the measured values surrounding the prediction location. The measured values closest to the prediction location have more influence on the predicted value than those farther away. IDW assumes that each measured point has a local influence that diminishes with distance. It gives greater weights to points closest to the prediction location, and the weights diminish as a function of distance, hence the name inverse distance weighted.

basic sorting algorithms implemented in golang

Mon, 04 Sep 2017 00:00:00 +0000

This post includes go-lang based implementation of some of the classic sorting algorithms.

This article primarily, has been written, as an academic exercise, to not forget the basic principles of sorting.

Bubble Sort

wiki

Bubble sort is perhaps the simplest of all sorting algorithms, the basic principle is to bubble up the largest (or the smallest) and then the second largest and then the third largest and so on. Each bubble takes the full sweep of the list, hence best-case, average-case as well as the worst-case performance are all O(n2)

reading and writing binary files in go lang

Tue, 29 Aug 2017 00:00:00 +0000

Reading and writing binary files can often be a fast and very efficient alternatives to csv. They obviously have their challenges, however in this post I intent to present a very basic example of saving models (struct) into binary file and later reading it.

package main

import (
 "log"
 "os"
 "encoding/binary"
 "bytes"
 "fmt"
 "math/rand"
 "time"
)

//this type represnts a record with three fields
type payload struct {
 One float32
 Two float64
 Three uint32
}

func main() {

 writeFile()
 readFile()

}

func readFile() {

 file, err := os.Open("test.bin")
 defer file.Close()
 if err != nil {
 log.Fatal(err)
 }

 m := payload{}
 for i := 0; i < 10; i++ {
 data := readNextBytes(file, 16)
 buffer := bytes.NewBuffer(data)
 err = binary.Read(buffer, binary.BigEndian, &m)
 if err != nil {
 log.Fatal("binary.Read failed", err)
 }

 fmt.Println(m)
 }

}

func readNextBytes(file *os.File, number int) []byte {
 bytes := make([]byte, number)

 \_, err := file.Read(bytes)
 if err != nil {
 log.Fatal(err)
 }

 return bytes
}

func writeFile() {
 file, err := os.Create("test.bin")
 defer file.Close()
 if err != nil {
 log.Fatal(err)
 }

 r := rand.New(rand.NewSource(time.Now().UnixNano()))

 for i := 0; i < 10; i++ {


 s := &payload{
 r.Float32(),
 r.Float64(),
 r.Uint32(),
 }
 var bin\_buf bytes.Buffer
 binary.Write(&bin\_buf, binary.BigEndian, s)
 //b :=bin\_buf.Bytes()
 //l := len(b)
 //fmt.Println(l)
 writeNextBytes(file, bin\_buf.Bytes())

 }
}
func writeNextBytes(file *os.File, bytes []byte) {

 \_, err := file.Write(bytes)

 if err != nil {
 log.Fatal(err)
 }

}

The code presented above will randomly populate 10 records of type payload and save it to a binary file, then it will read those 10 records as well.

Create linear color gradient in go

Mon, 28 Aug 2017 00:00:00 +0000

Go doesn’t have any builtin gradient functions to paint/fill the background of a raster, however it has all the required primitives one needs to create a very basic linear gradient.

Here is a basic code which defines a 256 x 256 image, then calculates the value of each pixel in the raster based on a linear interpolation formula.


import (
"image"
"image/color"
"image/png"
"log"
"os"
"os/exec"
)
var(
colorB = [3]float64{248, 54, 0}
colorA = [3]float64{254, 140, 0}
)
var(
width = 256
height = 256
max = float64(width)
)
func linearGradient(x, y float64) (uint8, uint8, uint8) {
d := x/max
r := colorA[0] + d * (colorB[0] - colorA[0])
g := colorA[1] + d * (colorB[1] - colorA[1])
b := colorA[2] + d * (colorB[2] - colorA[2])
return uint8(r), uint8(g), uint8(b)
}
func main() {
var w, h int = width, height
dst := image.NewRGBA(image.Rect(0, 0, w, h)) //*NRGBA (image.Image interface)
for x := 0; x < w; x++ {
for y := 0; y < h; y++ {
r, g, b := linearGradient(float64(x), float64(y))
c := color.RGBA{
r,
g,
b,
255,
}
dst.Set(x, y, c)
}
}
img, \_ := os.Create("new.png")
defer img.Close()
png.Encode(img, dst) //Encode writes the Image m to w in PNG format.
Show(img.Name())
}
// show a specified file by Preview.app for OS X(darwin)
func Show(name string) {
command := "open"
arg1 := "-a"
arg2 := "/Applications/Preview.app"
cmd := exec.Command(command, arg1, arg2, name)
err := cmd.Run()
if err != nil {
log.Fatal(err)
}
}

Here is how the generated image looks like

merge sort in python

Sun, 23 Jul 2017 00:00:00 +0000

Many useful algorithms are recursive in structure: to solve a given problem, they call themselves recursively one or more times to deal with closely related subproblems.
These algorithms typically follow a divide-and-conquer approach: they break the problem into several subproblems that are similar to the original problem but smaller in size, solve the subproblems recursively, and then combine these solutions to create a solution to the original problem.

The divide-and-conquer paradigm involves three steps at each level of the recursion:

Using Geotiff as datasource via gdal

Wed, 21 Dec 2016 00:00:00 +0000

Recently, I have been working on algorithms which needs elevation data as well as Land Cover data, with world coverage. Google has an excellent elevation API however free usage comes with a limit.

While searching, I came across a dataset in geotiff format for landcover as well as a processed version of world elevation. Elevation data comes in various resolution (250m,500m,1km), landcover is 500m .

So how do we read it ? In python its quite easy to use osgo/gdal library and read all bands. Geotiff is a rster file and values can be packed in every band (which is basically a 2d array).

How to create fishnets or geospatial grids

Sun, 11 Dec 2016 00:00:00 +0000

There are many use cases in GIS world, where the information has to be aggregated, an easy way to achieve this is via gridding or binning, where the area of interest is divided into small sections called grids or bins.

These sections are mostly of rectangular form (which can be easily converted into geotiffs), but in some cases even circles or hexagons are also used.

You can read a good tutorial from mapbox using Qgis with a mmqgis plugin here.

How to transform projections between Spherical Mercator and EPSG 4326

Sat, 10 Dec 2016 00:00:00 +0000

Projections in GIS are commonly referred to by their “EPSG” codes, these are identifiers managed by the European Petroleum Survey Group.

One common identifier is “EPSG:4326”, which describes maps where latitude and longitude are treated as X/Y values.

Spherical Mercator has an official designation of EPSG:3857. However, before this was established, a large amount of software used the identifier EPSG:900913. This is an unofficial code, but is still the commonly usedin many GIS systems.

How to Query a Shape file for Point inside a polygon using ogr python

Thu, 01 Sep 2016 00:00:00 +0000

Recently I was trying to build a quick geo lookup service in python, which could be used like an “info tool” in QGIS. This task is trivial in almost all geospatial databases, however I wasn’t able to find much online around querying a shape file.

In this post I will demonstrate a simple python code to query a shape file which contains world countries. The file can be downloaded from here.

How to read a csv file in go

Tue, 30 Aug 2016 00:00:00 +0000

One of the most common task for a programmer is either to read or write a csv file

Read a csv file

package main
import (
"bufio"
"encoding/csv"
"os"
"fmt"
"io"
)
func main() {
// Load a csv file.
f, \_ := os.Open("/path/to/my/csv/file.csv")
// Create a new reader.
r := csv.NewReader(bufio.NewReader(f))
//define seperator
r.Comma = ','
for {
record, err := r.Read()
// Stop at EOF.
if err == io.EOF {
break
}
// Display record.
fmt.Println(record)
// ... Display record length.
fmt.Println(len(record))
// ... Display all individual elements of the slice.
for value := range record {
fmt.Printf(" %v\n", record[value])
}
}
}

How to integrate Google container engine with Stackdriver with kubernaties

Thu, 04 Aug 2016 00:00:00 +0000

Most folks have been using Grafana or something similar to monitor Kubernaties cluster.

If you are using Google cloud container engine , then the standard unified place to monitor all your application and services is Slackdriver.

According to googles documentation, when you create a new container cluster using GUI or gcloud, Slackdriver is automatically configured with a sink, however It did not work out of the box for me hence this post :)

Well, the easiest way to check if Slackdriver is configured is to issue a command

Binary Search Tree in python

Mon, 01 Aug 2016 00:00:00 +0000

BST data structure supports many dynamic-set operations including

Search
Minimum
Maximum
Predecessor
Successor
Insert
Delete

These basic operations allow us to treat this data structure both as a dictionary and as a priority queue.

Basic operations on a binary tree takes time proportional to the height of the tree, O(lg n) [worst case] and even O(n) if the tree is a linear chain.

If you want to learn more about practical application of these trees check this post out.

Heap Sort in python

Mon, 25 Jul 2016 00:00:00 +0000

The (binary) heap data structure is an array object that we can view as a nearly complete binary tree.
Each node of the tree corresponds to an element of the array.
The tree is completely filled on all levels except possibly the lowest, which is filled from the left up to a point.
An array A that represents a heap is an object with two attributes:

length, which (as usual) gives the number of elements in the array.

Insertion sort in python

Fri, 22 Jul 2016 00:00:00 +0000

Insertion sort, is an efficient algorithm for sorting a small number of elements.

Insertion sort works the way many people sort a hand of playing cards. We start with an empty left hand and the cards face down on the table. We then remove one card at a time from the table and insert it into the correct position in the left hand.

To find the correct position for a card, we compare it with each of the cards already in the hand, from right to left.

How to install Ubuntu bash on windows

Thu, 07 Apr 2016 00:00:00 +0000

Microsoft announced at Build 2016 , about the new feature to run native Bash and GNU/Linux command-line tools

Gabriel Aul has just announced the release of the Windows 10 build #14316 to the Windows Insiders Fast-Ring

This build contains the first public release of Bash on Ubuntu on Windows and the underlying Windows Subsystem for Linux.

Turn on Developer Mode: Settings | Update & Security | For Developers | Check the Developer Mode radio button:
From the start menu, open “Turn Windows Features on or off”:
Scroll down and check the “Windows Subsystem for Linux (Beta)” feature:
Hit okay and reboot (required step)
Once rebooted, open a PowerShell/command prompt and run “Bash” and follow the simple prompts to accept Canonical’s license and kick-off the download of the Ubuntu image:
After download has completed, you’ll be able to start “Bash on Ubuntu on Windows” from the Start menu:

How to use Google Appengine Remote API for Java

Tue, 22 Mar 2016 00:00:00 +0000

Google App Engine Remote API enables programmers to access Google DataStore remotely from any python script or a Java Program.

Remote api essentially is a generic web service, which allows datastore to be accessed from outside the app engine’s environment therefore using this mechanism, users can either bulk insert data or modify existing data from their servers.

With the help of remote api, data from one datastore can be copied to data on another app engine instance as well.

Read GAE Admin Backups fromLevelDB format and export GAE Entities using bulkloader

Mon, 11 Jan 2016 00:00:00 +0000

Google datastore is pretty awesome when one needs a quick no-sql data storage. However recently I have experienced a problem in exporting my GAE Datastore as csv and in certain cases as a line delimited Json file. Its not very hard to do so and perhaps the easiest way to handle such thing is to write an export handler in you web app, however, there are alternative ways which I have highlighted below. 2. One of the easiest alternative is by using Datastore Admin . This tool will easily let you backup you GAE DataStore Entities to google cloud storage in the same project which can later be downloaded locally, by using cloud console or gsutil like this gsutil cp -R /gs/your_bucket_name/your_path /local_target 4. Then there is Remote API for python and Java, which perhaps was created to modify the datastore directly via code from your local machine 6. Finally there is a python utility called bulkloader.py which is coupled with remote_apii , this utility does require python sdk to be installed and added to your system path.

Serving raster layers on Google Cloud Platform

Mon, 21 Sep 2015 00:00:00 +0000

In this blog post, I will write about using Google cloud storage as a Raster Tile Server for static imagery.

In the GIS domain, various techniques are used to add custom raster overlay on top of a base maps, or to even use custom imagery, as a base map itself.

This approach is also useful if you have a large quantity of satellite or aerial imagery, that you need to serve at scale onto a Google map or any other GIS tool.

Install all Go project dependencies in one command

Tue, 25 Aug 2015 00:00:00 +0000

So if you are looking to compile you go project on your server, you would probably need to worry about any third party dependencies.

Here is quick recursive way to do that

go get ./…

Hope this helps

Bubble-sort in python

Thu, 23 Jul 2015 00:00:00 +0000

Bubble sort is a sorting algo that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order.

It is a popular, but inefficient sorting algo, it has worst-case and average complexity both О(n2), where n is the number of items being sorted.

Here is an implementation in python

 count = len(B)
 for i in xrange(count):
 for j in xrange(count-1,i,-1):
 #print "compairing %i with %i"%(B[j],B[j-1])
 if B[j] < B[j - 1]:
 temp = B[j]
 B[j] = B[j - 1]
 B[j - 1] = temp
 #print "Swapping %i with %i"%(B[j],B[j-1])
 #print "Transformed Array: " , B


B = [6,5,3,1,8,7,2,4]
print "Unsorted: ", B
bubbleSort(B)
print "Bubble Sorted: ", B

Hope this helps

ultimate developer and power users tool list for mac and linux

Sat, 07 Feb 2015 00:00:00 +0000

This is a collection of tools and utilities which I have found indispensable as an engineer. Each has a distinct purpose, and I probably touch each at least a few times a week. These tools save me time and I hope that you will find some of them useful as well.

Productivity

s-tui s-tui is a terminal UI for monitoring your computer. s-tui allows to monitor CPU temperature, frequency, power and utilization in a graphical way from the terminal.
Cockpit is a server manager that makes it easy to administer your GNU/Linux servers via a web browser.

Security

https://www.tinc-vpn.org/ Virtual Private Network (VPN) daemon that uses tunnelling and encryption to create a secure private network between hosts on the Internet.

Fun

https://github.com/abishekvashok/cmatrix Matrix digital rain with CMatrix on a Linux or Unix terminal .

Automation

FunnelScripts Facebook Adverts.

Creating Isochrones and Isodistances using Googles Direction Search API

Mon, 29 Dec 2014 00:00:00 +0000

Introduction

Isochrones are curves of equal travel time from a certain point of origin, another way of saying this would be that an Isochrone is an isoline for travel time, if the weighting factor is changed form time to distance, then the resulting curve us called an Isodistance.

In this post I will present a rough way to create an Isochrone and an Isodistance using google’s directions API.

Tilestache on google maps

Fri, 26 Dec 2014 00:00:00 +0000

Introduction

In this post I will demonstrate how to add custom TileStache map tiles on google maps, using google maps JavaScript API V3. TileStache has emerged as one of the easiest way to render your own map .There are many examples out there on creating basic tiles and then adding them on top of Leaftlet or Openlayers. In this post I will add them as an overlay on Google Maps.

Merge multiple Shapefiles using OGR2OGR in windows Linux or OSX

Mon, 22 Dec 2014 00:00:00 +0000

Introduction

This post is aimed at providing assistance to folks who are trying to merge many shapefiles into one single file in either windows or linux environment. Stuff like this may seem obvious to power users of GDAL/OGR, but not to those that are just new to using these great free tools.

Merging Shape (*.shp) Files on Windows

Essentially, these commands will grab every shapefile in a directory, and merge them into a single file called “merged.shp”.

HTML Geolocation and Altitude

Sun, 21 Dec 2014 00:00:00 +0000

HTML5 Geolocation is a feature which allows the browser on a computer or a mobile phone, to acquire the position from the wifi,2g/3g/4g network or GPS.

The HTML Geolocation API is used to get the geographical position of a user. Since this can compromise user privacy, the position is not available unless the user approves it. The simplest way to use it through navigator.geolocation object ``` if (navigator.geolocation) { navigator.geolocation.getCurrentPosition(showPosition);

Classes and Inheritance in EcmaScript 6 (ES6 Harmony)

Sun, 30 Nov 2014 00:00:00 +0000

So if you are a JavaScript geek and haven’t yet heard,(if every one is listening to ECMA announcements, who’s gonna drink beer :) ) ECMA 6 feature set has been drafted,its feature set is frozen, it is mostly being refined now. You can already program in it and compile it to current JavaScript . The JavaScript frameworks AngularJS and Ember.js will be based on it (with ways to opt out). Again, via cross-compilation.

longest palindrome in a string

Wed, 15 Oct 2014 00:00:00 +0000

def isPailenDrome(s):
 if len(s)==1:
 return False
 L = len(s)
 for i in range(L):
 if s[i] != s[L-1-i]:
 return False
 return True


def longestPalindrome(s):
 L = len(s)
 if len(s)<=1:
 return s
 if isPailenDrome(s):
 return s
 p = {}
 for u in range(L):
 for v in range(u+1,L+1):
 k = s[u:v]
 # print k,isPailenDrome(k)
 if isPailenDrome(k):
 p[len(k)] = k

 if len(p) > 0:
 return p[sorted(p,reverse = True)[0]]
 return s[0]

print two-dimensional array in spiral order

Wed, 15 Oct 2014 00:00:00 +0000

So I saw this problem in a book today about printing a 2d matrix in spiral order

Here are two solutions to it

Solution one.

def printSpiralTL(m,x1,y1,x2,y2):
 for i in range(x1,x2):
 print m[y1][i]
 for j in range(y1+1,y2+1):
 print m[j][x2-1]

 if x2-x1 > 0:
 printSpiralBL(m, x1, y1 + 1, x2-1, y2)


def printSpiralBL(m,x1,y1,x2,y2):
 for i in range(x2-1,x1-1,-1):
 print m[y2][i]
 for j in range(y2-1,y1-1,-1):
 print m[j][x1]
 if x2-x1 > 0:
 printSpiralTL(m, x1+1, y1, x2, y2-1)

m = [

 [1, 2, 3, 4],
 [5, 6, 7, 8],
 [9, 0, 1, 2],
 [3, 4, 5, 6],
 [7, 8, 9, 1]

 ]

Output:

merge two sorted arrays in python

Sat, 11 Oct 2014 00:00:00 +0000

Here is a quick code snippet to merge two sorted arrays in python

 merged = []
 l = 0
 r = 0
 for i in range(len(a)+len(b) ):
 lval = None
 rval = None

 if l < len(a):
 lval = a[l]
 if r < len(b):
 rval = b[r]

 if (lval < rval and rval and lval) or rval == None:
 merged.append(lval)
 l+=1
 elif (lval >= rval and rval and lval)or lval == None:
 merged.append(rval)
 r+=1

 return merged

print merge([3,5],[2,4])

Update the locate DB on OS X

Wed, 10 Sep 2014 00:00:00 +0000

Apparently out OS X does not have an updatedb command like linux has, so I was stumped on how to update the locate database.

I have quickly added this command here, incase I need to use it again.

sudo /usr/libexec/locate.updatedb

How to print the Fibonacci Sequence in Python

Sat, 09 Aug 2014 00:00:00 +0000

The Fibonacci numbers are the sequence of numbers defined by the linear recurrence equation

 ![ F_n=F_(n-1)+F_(n-2) ](http://mathworld.wolfram.com/images/equations/FibonacciNumber/NumberedEquation1.gif) with ![F_1=F_2=1](http://mathworld.wolfram.com/images/equations/FibonacciNumber/Inline2.gif) and ![F_0=0](http://mathworld.wolfram.com/images/equations/FibonacciNumber/Inline3.gif)

So in simple terms a method to compute fibonacci number for nth place looks like this

 if n == 0 or n ==1:
 return n
 else:
 return fibonacci(n-1)+fibonacci(n-2)

here is quick test

 print i," : ",fibonacci(i)
#This will print
0 : 0
1 : 1
2 : 1
3 : 2
4 : 3
5 : 5
6 : 8
7 : 13
8 : 21
9 : 34

or an inline method like this print [fibonacci(i) for i in range(11)] will result

Using ElasticSearch for Spatial Search tutorial

Sun, 20 Jul 2014 00:00:00 +0000

In this post I will demonstrate using ElasticSearch to spatially query records and filter them by attributes.

ElasticSearch is built on top of Lucence which in version 4.0 supports Spatial query features, for those interested here is an example and link to javadocs.

You will need to install ElasticSearch, read about installing it here, also install marvel plugin for configuration and testing.

For this demonstration I have used data from Geofabrik. I have used point.shp file from Great Britan but you can use data from any other country as well.

CCS3 only Loading Icon

Sun, 13 Jul 2014 00:00:00 +0000

I generally have been using loading gifs in my work most of the time to inform the user that the resources are being fetched asynchronously from the server.

Ajaxload website is perhaps one of the most used site to download a suitable gif.

In this post I will demonstrate a css3 only way to create a nice loading simulation

Basic Code

We will use nested divs to create the loading animation control ```

How to install and configure grunt on mac Osx

Sat, 12 Jul 2014 00:00:00 +0000

This post is intended to assist folks who are trying to install and work with grunt on mac osx

Install Node.js and npm with Homebrew

First, install Homebrew by typing in the following command ruby -e “$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

Then, type in brew update to ensure your Homebrew is up to date.

brew update

Run

brew doctor

to make sure your system is all good.

Follow any other recommendations from brew doctor.

Normalizing Ranges of Numbers

Wed, 09 Jul 2014 00:00:00 +0000

Range Normalization is a normalization technique that allows you to map a number to a specific range.

Lets say that we have a data set where the values are in a range of 1 to 10, however we wish to normalise it to a range between 0 and 5

Mathematically speaking the equation comes down to

translated to Python

class Normaliser:
def \_\_init\_\_(self,dH,dL,nH,nL):
self.dH = dH
self.dL = dL
self.nH = nH
self.nL = nL
def normalize(self,x):
return ((x - self.dL) / (self.dH - self.dL)) * (self.nH - self.nL) + self.nL
def denormalize(self,x):
return ((self.dL - self.dH) * x - self.nH * self.dL + self.dH * self.nL) / (self.nL - self.nH)
if \_\_name\_\_ == "\_\_main\_\_":
norm = Normaliser(10,1,5,0);
for a in range(1,11):
x = norm.normalize(a);
y = norm.denormalize(x);
print str(a) + " : " + str(x) + " : " + str(y)

The results

Install tile-stache on OsX Mavericks

Tue, 08 Jul 2014 00:00:00 +0000

This is quick tutorial about installing Tilestache library in OSX Mavericks.

Step 1

Make sure Developer tools are installed xcode-select –install

Then add these flags to tell xcode to use python like rest of the world does

export CFLAGS=-Qunused-arguments

export CPPFLAGS=-Qunused-arguments

Finally type in sudo easy_install tilestache

Thats it all done, you might see some warnings but thats fine ignore them .

Read the introduction here to get started

Hope it helps.

how to make a web crawler in python

Sat, 01 Feb 2014 00:00:00 +0000

Here is a very simple web crawler in python

import sys, thread, Queue, re, urllib, urlparse, time, os, sys
dupcheck = set()
q = Queue.Queue(100)
q.put("http://www.varunpant.com")
def queueURLs(html, origLink):
 for url in re.findall(''']+href=["'](.[^"']+)["']''', html, re.I):
 link = url.split("#", 1)[0] if url.startswith("http") else '{uri.scheme}://{uri.netloc}'.format(uri=urlparse.urlparse(origLink)) + url.split("#", 1)[0]
 if link in dupcheck:
 continue
 dupcheck.add(link)
 if len(dupcheck) > 99999:
 dupcheck.clear()
 q.put(link)
def getHTML(link):
 try:
 html = urllib.urlopen(link).read()
 print link
 # open(str(time.time()) + ".html", "w").write("" % link + "\n" + html) 
 queueURLs(html, link)
 except (KeyboardInterrupt, SystemExit):
 raise
 except Exception:
 pass
while True:
 thread.start_new_thread( getHTML, (q.get(),))
 time.sleep(0.5)

Ternary search tree

Sun, 26 Jan 2014 00:00:00 +0000

In computer science, a ternary search tree is a type of prefix tree where nodes are arranged as a binary search tree. Like other prefix trees, a ternary search tree can be used as an associative map structure with the ability for incremental string search. However, ternary search trees are more space efficient compared to standard prefix trees, at the cost of speed. Common applications for ternary search trees include spell-checking and auto-completion.

As with other trie data structures, each node in a ternary search tree represents a prefix of the stored strings. All strings in the middle subtree of a node start with that prefix.

Gheat Java – Heat maps

Fri, 24 Jan 2014 00:00:00 +0000

A heat map is a graphical representation of data where the individual values contained in a matrix are represented as colors.

This article will attempt to explain the process or creating and using GHEAT-JAVA, which is a port of famous aspen based gheat and took great inspiration from Gheat.net

Writing a service which would serve heat map tiles is a bit tricky,there are three major components involved

The client part i.e. some kind of mapping library which has a concept of layer, I chose Google maps.
The data source part, i.e. a spatially aware database or an in memory data structure, I have used postgres ,an in memory quad tree and a flat file as data sources.
The renderer part or basically the code which excepts requests , parses tile bounds, fetches data and then renders gradients on the tile and later colorizes them.

The Tiling layer (Client part)

Google maps allows developers to add a custom layer , the code looks like this

Raphael-js-tutorial-part-II

Wed, 25 Dec 2013 00:00:00 +0000

This is second part of the tutorial about getting started with Raphael.js. To see this first part go here.

Writing Text with Raphael

Some code first ;)

var canvas = Raphael(0, 0, 250, 250 );

var t1 = canvas.text(50, 50, *"Some text Goes here"*);

var t2 = canvas.text(60,90,"First line \n Second Line \n Third line");

var t3 = canvas.text(214, 140, "1079").attr({"text-anchor":"middle",'font-size':16,"font-family":"arial","fill":"#fff"});

In the above examples canvas.text will create a simple text element at 50,50. Strangely VML /SVG do not have Line breaks therefore the programmer is responsible for creating new lines,in most cases appending** ‘\n’** does the trick.

Turn Off Autocomplete for Input

Sun, 01 Dec 2013 00:00:00 +0000

The autocomplete attribute specifies whether or not an input field should have autocomplete enabled.

Autocomplete allows the browser to predict the value from locally saved history/cache. When a user starts to type in a field, the browser should display options to fill in the field, based on earlier typed values.

Note: The autocomplete attribute works with the following types: text, search, url, tel, email, password, datepickers, range, and color.

Embedding Flash,Quicktime,Windows Media,Silverlight or HTML5 Video

Tue, 01 Oct 2013 00:00:00 +0000

Flash Object

This is quick Snippet which demonstrate how to embed flash object in a web page.

<object type="application/x-shockwave-flash"
 data="path-to-my-flash-file.swf"
 width="0" height="0">
 <param name="movie" value="your-flash-file.swf" />
 <param name="quality" value="high"/>
</object>

Quicktime

This is quick Snippet which demonstrate how to embed quicktime object in a web page

<object classid="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B"
 codebase="http://www.apple.com/qtactivex/qtplugin.cab"
 width="200" height="16">
<param name="src" value="pathToMyMovie.mov" />
<param name="autoplay" value="true" />
<param name="pluginspage" value="http://www.apple.com/quicktime/download/" />
<param name="controller" value="true" />
<!--[if !IE]> <-->
 <object data="movie.mov" width="200" height="16" type="video/quicktime">
 <param name="pluginurl" value="http://www.apple.com/quicktime/download/" />
 <param name="controller" value="true" />
 </object>
<!--> <![endif]-->
</object>

Windows Media

This is quick Snippet which demonstrate how to embed Windows Media object in a web page.

Mod Proxy equivalent in IIS using ARR and URL Rewrite Module

Sun, 25 Aug 2013 00:00:00 +0000

IIS7 is quite modular, it is shipped with lots of goodies as separate modules and together it is now one of the most powerful and flexible web server.

In this post I intent to cover how we can easily configure ARR and URL Rewrite Module to get a similar functionality as of Mod Proxy in Apache.

Here I will demonstrate configuration of a reverse proxy which according to the definition is

Reverse proxy is a type of proxy server that retrieves resources on behalf of a client from one or more servers. A general use case to configure such proxies could be to handle cross domain Ajax requests, so basically if I would like to call a service hosted as http://anotherdomain.com/service from http://localdomain/service I would need to configure a proxy which will request resources from anotherdomain.com/service on behalf of localdomain ### Configuration

Signing android release apk from the command line (via ant)

Sun, 25 Aug 2013 00:00:00 +0000

This post is probably out too late ,as almost all IDE’s these days (which support android development) ,probably have an Integrated release signing or debug signing utility/wizard built in, but if somebody is using an old IDE or perhaps want to integrate release in a CI(continues integration) environment , this tutorial might come in handy.

Basically one has to sign an apk either with a debug key (which is generally present in your .android folder) or a create a fresh application specific keystore , to know more go here

Importing CSV File Into SQL SERVER Database using BULK INSERT

Mon, 11 Mar 2013 00:00:00 +0000

Importing data into a database from a delimited file is perhaps one of the most common tasks that one might have to perform. SQL server gives us an import utility which supports various data sources and has an intutive interface as well,however there is another way which can be utilized to quickly get the job done, its called BULK INSERT

BULK INSERT is a SQL command which can be typed in management console,takes various parameters to control the import and is very simple to use.

Importing Exporting CSV Files in PostgreSQL Databases via COPY

Mon, 11 Mar 2013 00:00:00 +0000

This is going to be a short article which will illustrate importing and exporting a table from or to a csv file using PostgreSQL COPY command.

Importing a table from CSV

Assuming you already have a table in place with the right columns, the command is as follows

COPY FROM ‘/path/to/csv/SourceCSVFile.csv’ DELIMITERS ‘,’ CSV;

Exporting a CSV from a table.

COPY TO ‘/path/to/csv/TargetCSVFile’ DELIMITERS ‘,’ CSV;

Raphael JS Tutorial - Part I

Sun, 10 Mar 2013 00:00:00 +0000

Raphael.JS is a SVG/VML library which helps you to create quick vector shapes and images. Its very small and compact (only 86kb),easy to use,well documented and works in all browsers and yes even IE. Here is a list of all major browsers this library works on: Chrome 5.0+ Firefox 3.0+, Safari 3.0+, Opera 9.5+ and Internet Explorer 6.0+

,finally its distributed under MIT license. In this tutorial ,I intend to introduce basics of this library and help you get started.

How to configure Apache mod_wsgi

Tue, 26 Feb 2013 00:00:00 +0000

I am a big fan and user of python. one of the most popular ways to create quick web app in python is via using mod wsgi.

The aim of mod_wsgi is to implement a simple to use Apache module which can host any Python application which supports the Python WSGI interface.

The module would be suitable for use in hosting high performance production web sites, as well as your average self managed personal sites running on web hosting services.

Serve the contents of any directory with Python's SimpleHTTPServer

Fri, 08 Feb 2013 00:00:00 +0000

Generally, when I am in a middle of prototyping a concept or in a need of quickly executing Ajax requests or using browser features which would need the page to be hosted on a web server, I use Python’s SimpleHTTPServer module.

Python’s SimpleHTTPServer is a great way of serve the contents of the current directory,all one needs to do is change directory and execute a command which will expose all contents as if they were hosted in a web page.

Avoid console errors in browsers that lack a console

Wed, 30 Jan 2013 00:00:00 +0000

I love JavaScript and code a lot in it .Since I code, I also encounter problems and bugs from time to time and therefore need a Debugger and a debug mechanism to view whats going on.

In good old days when I learned this language, I used JavaScript’s inbuilt alert mechanism to view the value of a variable or a property of an object. This was a terrible mechanism, calling alert was blocking, one had to press OK to continue and if you had to take a look inside an array then well it was emotionally an overwhelming task is all I would say here.

sqlite3 Bulk Import CSV from command line

Tue, 29 Jan 2013 00:00:00 +0000

I absolutely love SQLite, be it windows, linux or mac, this light weight database never stops to amaze me.

Few days ago I wanted to import a chunk of CSV data, which was 4 GB in size into a table in SQLite.

I generally use Firefox ’s sqlite-manager plug-in for usual tasks with SQLite database ,hence decided to use the import interface .

I have had a very good experience with this GUI tool and it has rarely failed me, but this time I was disappointed.

Install Apache Cassandra

Sun, 27 Jan 2013 00:00:00 +0000

Cassandra is an Open Source Distributed Data Persistence system which is designed for storing and managing large amounts of data across servers.

To quote elevator pitch by Eben Hewitt

Position div in the center of the page using css

Sun, 27 Jan 2013 00:00:00 +0000

When I first started web programming, creating a center aligned div was one of the most common task that I saw myself doing.

since div is a block element, i.e. it takes up the full width available, and has a line break before and after it, it can easily be centered using relative styling

{
margin-left:auto;
margin-right:auto;
width:70%;
background-color:#b0e0e6;
}

However lately I have preferred using absolute positioning technique over relative, this works for all browsers and is best for login screens or alert messages over a translucent shim.

A guide to hosting in Red Hats OpenShift PaaS

Fri, 25 Jan 2013 00:00:00 +0000

In this post,I am going to write about OpenShift, which is Red hat’s free, auto-scaling Platform as a Service (PaaS) for applications.

OpenShift to me is very similar to Google’s app engine in some ways,but openshift’s offerings are quite diverse, for instance support for ruby, php, Perl, node.js, etc..

Openshift is not like a traditional VPS hosting , although once registered with them, user does get a shell access,but its quite limited , instead OpenShift has a concept of gears and cartridges.

Basic authentication in web.py via attribute

Wed, 23 Jan 2013 00:00:00 +0000

Here I demonstrate the process of Basic Authentication in web.py python web framework.

There is a proof of concept article provided in the main site,however I just thought doing the same via an attribute might be a cleaner solution.

HTTP Basic authentication implementation is one of the easiest ways to secure web pages because it doesn’t require cookies, session handling, or the development of login pages. Rather, HTTP Basic authentication uses static headers which means that no handshakes have to be done in anticipation,however the n the credentials are passed as plain-text and could be intercepted.

Cross browser drop shadow with CSS3

Wed, 23 Jan 2013 00:00:00 +0000

When css3 arrived, one of the goodies that I found was, the inclusion of Drop Shadow effect, namely **Box Shadow **and Text Shadow.

Here I present a cross browser utility css class which can be used for a drop shadow effect, without any image.

.shadow {
 /* For IE 8 */
 -ms-filter: "progid:DXImageTransform.Microsoft.Shadow(Strength=4, Direction=135, Color='#000000')";
 /* For IE 5.5 - 7 */
 filter: progid:DXImageTransform.Microsoft.Shadow(Strength=4, Direction=135, Color='#000000');
 -moz-box-shadow: 3px 3px 4px #000;
 -webkit-box-shadow: 3px 3px 4px #000;
 box-shadow: 3px 3px 4px #000;
}

For cross browser text shadow effect ,I found a nice article here.

Cross browser CSS3 border-radius (rounded corners)

Tue, 22 Jan 2013 00:00:00 +0000

When I started programming and had to begin designing my first user interface in HTML, I was always puzzled as to why are all visual elements in HTML rectangular. I soon learned that in those days if one would want a circle to be drawn on a page, then the only way possible was using an image, the same was true for drawing elements with rounded corners.

Thankfully HTML5/CSS3 guys were listening and the latest css3 standard supports defining the corner radius of a circle, this can be used to make an element look like a circle too if you want.

Cross Browser Opacity or Transparency

Tue, 22 Jan 2013 00:00:00 +0000

Css has a very useful property called Opacity, which basically is a measure of transparency of an element.

All modern browsers Yes yes even IE has support for it.

In most browsers the value is between 0 minimum [transparent] i.e not visible to 1 maximum [opaque] i.e. completely visible

In IE the value is between 0 and 100 ,don’t ask why they just like to make us unhappy.

Here I present a helper css class which will work in all browsers.

Installing Redis on Ubuntu

Sun, 20 Jan 2013 00:00:00 +0000

Redis is an open source, advanced key-value store. Installing it on Linux debian platforms is pretty easy.

There are two ways of getting this done, one is perhaps an easy and less verbose method and it involves using an alternative repository Dotdeb.

A while ago I had posted a tutorial about installing redis from the googlecode repo, but things have changed since then and here I post a fairly latest way of installing it.

gzip compression in apache using mod_deflate

Sat, 19 Jan 2013 00:00:00 +0000

HTTP Compression is a very simple and effective way to save bandwidth and improve web applications performance over network.

Output compression is basically a process of compressing web servers response by using a loss-less compression algorithm called gzip.

This technique is fairly modern and almost all modern browsers honor it, however if a page is requested from a browser which does not send a header Accept-Encoding: gzip,deflate then the response comes back uncompressed.

Start Stop Restart Apache 2 Web Server

Sat, 19 Jan 2013 00:00:00 +0000

I have been using Linux environment a lot lately, particularly for hosting my web experiments and other application. One of the biggest and most searched question for newbies have been

How do I restart Apache 2 Web Server under Debian / Ubuntu Linux or UNIX operating systems?

In this post I simply attempt to lay this down for my and their benifit.

Start Apache2 # sudo /etc/init.d/apache2 start

Stop Apache2 # sudo /etc/init.d/apache2 stop

Factorial in python

Tue, 14 Aug 2012 00:00:00 +0000

Mathematically, the formula for the factorial is as follows. If n is an integer greater than or equal to 1, then n ! = n ( n - 1)( n - 2)( n - 3) … (3)(2)(1) If p = 0, then p ! = 1 by convention.

def factorial(n):
 if n == 0:
 return 1
 else:
 return n * factorial(n-1)

Hope this helps

Auto Complete with Redis (Python)

Sun, 06 May 2012 00:00:00 +0000

This is a quick port of auto complete implementation in ruby using Redis by antirez.

I like python and had little time to burn today, so here goes:

The file used for input is female-names.txt

Hope it helps :)

How To Install and use Python Web.py framework on Windows

Sun, 06 May 2012 00:00:00 +0000

Web.py has been one of my favorite web frameworks as its pretty easy to get cracking on it.

It’s super quick to install and one can come up with a prototype and rapid web services in matter of minutes.

Install on windows

If you haven’t configured easy_install on windows, then read this article.

Once easy_install has been configured believe it or not, all you have to do is open a command prompt and type

How to setup easy_install on Windows

Sun, 06 May 2012 00:00:00 +0000

If one has been using python, then installing various libraries and modules is basically a breeze using easy_install utility, however for folks using windows, easy_install utility has to be setup properly before using it.

First lets make sure that python is properly installed and PYTHON_HOME environment variable is configured:

Install Python on Windows

If not already installed download python installer from here.

After it’s done downloading, double click to run the installer, and select default options (unless you have other custom needs of course ).

Find Longitude and Latitude in Google Maps

Sun, 15 Apr 2012 00:00:00 +0000

This post is basically a way of quick appreciation to the Google maps Team, they are obviously a bunch of caring, loving people ,who make useful (although surreptitious) tools for the betterment of Geek Kind.

So as most of you may have accidently clicked a mysterious looking link at the bottom of your Google maps page ( on the left hand panel)

This awesome looking link opens up a popup which lets you choose wonderful goodies which makes your Google maps page more useful than it already is:

How to set up Redis in Ubuntu Linux

Sat, 14 Apr 2012 00:00:00 +0000

Redis is an open source, advanced key-value store, and is quickly picking up momentum in real-time software development , it is now a well known and trusted product and can be used in various problem scenarios as a No SQL implementation.

Redis is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.

Here is quick guide to Install Redis in Ubuntu 10.04, and it should be similar for higher versions and similar deb environment.

Installing Ubuntu Linux in VMware and VMwareTools

Mon, 09 Jan 2012 00:00:00 +0000

I have been using Ubuntu for last two years as a deployment environment for my pet projects, however recently, after having installed “Natty Narwhal” on one of my old ‘HP’ laptop I moved into using Ubuntu as a full time development environment.

There are times when I need more than one deployment units and since I use Linodeas my primary deployment VPS host, I sometime need to test the perf of my software locally thus there came a need of replicating an exact or close to exact “Deployment Environment”

LIMBO Game Review

Wed, 19 Oct 2011 00:00:00 +0000

LIMBO is a horrifically beautiful, monochrome or rather a gray-scale purgatory painted perhaps while watching Tim burton movie on the side. It was published initially in Jul 2010 by Microsoft Game Studios(XBLA) and Playdead(PSN, Windows), and then later released for Windows platform by Steam.

The primary character of the game is a boy, who wakes up right at the beginning of the game i.e while you are trying to figure out WTF is happening or wonder if you graphics driver (windows platform) screwed up or something, but there as you are fiddling with the movement buttons in keyboard you will see pair of bright white eyes flickering, and that’s when you start falling in love with the game and the care of detail added in a game which is totally unlike other in its league.

VPS Hosting Past and Present

Tue, 27 Sep 2011 00:00:00 +0000

I had been hosting this blog in the past for an extremely competitive (read cheap) price here at Arvixe . I was using ASP.net based blogging software called BlogEngine. over and all I will describe my experience as pleasant. Arvixe is a great Hosting Provider, has good up time and has plans which are easy on the pocket, and does almost all the common stuff like emails and cpanel ,blah blah that other hosting provider do, but kinda does it on a low price. I was a happy blogger for an year although I could only manage close to 8 post and and few demos in that time.

Web Sockets in HTML 5

Mon, 10 Jan 2011 00:00:00 +0000

HTML5 WebSockets, defines a full-duplex communication channel that operates through a single socket over the web. WebSocket is not just another incremental enhancement to conventional HTTP communications, it represents a large advance, especially for real-time, event driven web applications.

Normally when a browser visits a web page, an HTTP request is sent to the web server that hosts that page. The web server acknowledges this request and sends back the response. In many cases—for example, for stock prices, news reports, ticket sales, traffic patterns, medical device readings, and so on—the response could be stale by the time the browser renders the page.

Water Simulation

Sat, 25 Sep 2010 00:00:00 +0000

Its been a while since my last post, had been busy with office work…sigh!!!

Anyways, I was poking around web to come up with interesting water simulation techniques, as you could see in many games these days, so I did find a reference to an old C-based technique, after little refinement, what I have is a water simulation which uses a very old algorithm based on two heightmaps.

As always it’s a grid based animation which divides the screen into a mesh(more slices better this simulation looks), I use a jagged array in c# to do this (load it with a texture of 640 X 480 dimension ), to animate I use another array of same dimensions, now to make every thing move I kinda do something like this

Liquid Particles

Sat, 03 Jul 2010 00:00:00 +0000

After ages of constantly being one of the most used browser as well as a serious pain in Butt!!! IE is finally about to mature into something good and perhaps a useful software , with its support to most of the standards being used today , IE will join back the league of web 3.0 browsers, hopefully very soon

So I was going through various experiments done with Canvas and came across a great example on Liquid Particle physics simulation, which amazingly is written in JavaScript and Canvas element, I was so mesmerized by the application that I had to port it to SilverLight, using WritableBitmap.

Image Carousel

Tue, 29 Jun 2010 00:00:00 +0000

Here is another of many JavaScript based Image Carousel, I had seen many similar to these made in SilverLight and Flash, I came across a wonderful carousel made in SilverLight sometimes back which was very fluid in behavior and could easily be customized and configured to take various shape and form.

I have managed to port it to JavaScript, it works best on chrome or FF, hope this would be fun to play with.

I-Phone Scroll

Fri, 18 Jun 2010 00:00:00 +0000

One of the amazing features of i-phone user interface is smooth panning/scrolling animation.

I-phone “List Scrolling” perhaps gives a very funky and usable List –View to its users and allows them to scroll up and down the interface without any need of a scroll bar.

This interface is sensitive to the push speed and also shows traces of resilience.

I have been experimenting with various techniques to bring out similar effect using JavaScript and HTML, I am not quite sure if this would be useful in its present form but with some modifications may be this sample could prove its worthiness somewhere.

Data URI and IE

Tue, 15 Jun 2010 00:00:00 +0000

Few days ago I was experimenting with a nifty technique of embedding images in web pages by base64 encoding them first and then using a standard known as Data URI Scheme, which basically defines a method of assigning a ‘src’ of an image tag as a base64 serialized string, like this:


background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABkAAAAUBAMAAACKWYuOAAAAMFBMVEX///92dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnZ2dnYvD4PNAAAAD3RSTlMAACTkfhvbh3iEewTtxBIFliR3AAAAUklEQVQY02NgIBMwijgKCgrAef5fkHnz/y9E4kn+/4XEE6z/34jEE///A4knev7zAwQv7L8RQk40/7MiggeUQpjJff+zIpINykbIbhFSROIRDQAWUhW2oXLWAQAAAABJRU5ErkJggg==");

Although this technique could save some server round trips, however Microsoft ver. (IE < 8). does not support this scheme even though its a standard, which then makes this technique unfavorable to use as its not cross browser.

Notepad++ with Python

Tue, 15 Jun 2010 00:00:00 +0000

After reading an excellent article by Kazi Manzur Rashidon setting up a development environment for Iron Ruby using Notepad++, I was immediately struck with an idea of using the same excellent tool with Python 2.6.

Now don’t get me wrong here, theoretically there is nothing wrong with IDLE, but having a light weight IDE for those who don’t want to use Pydevplugin for Aptanaor Eclipse, I think Notepad++ is indeed a nice little dev tool.

Hello World!

Sat, 12 Jun 2010 00:00:00 +0000

After long period of wait, here it is my very first and personal Blogging Space.

I have been hoping to go online for about an year now, but then there always were events happening around to prevent this immense desire of mine.

I intend to blog about .net in general , JavaScript, Silverlight, Animation and maybe some other cool stuff .

Hope to update this space again.

Cheers!!!

– Varun

Varun Pant

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