Python3 Invalid escape character ‘\’

Hello, everyone! Recently, I encountered an issue while upgrading my Python version from 3.8 to 3.12.

Here’s a snippet of my code:

my_string = '%'

if my_string == '%':
    my_string = my_string.replace('%', '\%')

Upon running this code in Python 3.12, I received a SyntaxWarning about an invalid escape sequence ‘%’:

<>:4: SyntaxWarning: invalid escape sequence '\%'
<ipython-input-9-9dfd61838f57>:4: SyntaxWarning: invalid escape sequence '\%'
  my_string = my_string.replace('%', '\%')

Please note that this is a warning and not an error.

The change in Python 3.12 is related to the addition of this syntax to deprecated warnings, which started in Python 3.6. It has now been elevated to SyntaxWarnings to bring attention to it within the Python community.

To resolve this warning, simply add an extra ” to escape the escape character. Here’s the corrected line:

my_string = my_string.replace('%', '\\%')

That’s it! Happy coding!

How to extract a gzip file or ungzip in Mac OS via terminal

Hello, everyone. Today, I was trying to extract or ungzip a file compressed using gzip compression on Mac OS. Unfortunately, I couldn’t do it by extracting, as there was no predefined UI option that appeared after right-clicking on the file.

Gzip compression comes into play to compress HTTP content before delivering it to the client. Hence, gzip has become popular nowadays. If you are using nginx for your servers, you might have seen “gzip on” in your nginx.conf file.

Let’s address our problem of extracting a .gz file. I have to do it the old way, the “Terminal Way (which I always prefer),” to extract the gzipped file.

To Extract a gz file:

gzip -d path-to-your-file.gz

Here, -d stands for uncompress/decompress.

To compress a file using gzip compression, use the following command:

gzip -k <path-to-your-file>

Here, -k stands for compress and keep the original file. If you don’t want the original file, then use:

gzip <path-to-your-file>

Please note that the above command will modify your original file, so be aware of it while using it without any options.

To test a compressed file, use the following command:

We can verify our compressed file by using the following command

gzip -t <path-to-your-file> -v

-t stands for test, and -v stands for verbose. This will return output like:

<your-file-name>:   OK

So far, we have seen how to compress and decompress gzip files. Can we gzip a directory using gzip alone? Unfortunately, you can’t compress a directory using gzip. Don’t worry; there is a hack for that too.

To compress a directory using gzip, when you try to compress a directory using -r with gzip, it compresses all files inside a directory with gzip compression.

For example, if you have a directory structure like this:

home
   |
   test/
        -- fileone.csv
        -- filetwo.csv
        nestedtestdir/
            -- nsfilefileone.xlsx
            -- hello.txt

What happens when you fire this command:

After this, the directory structure becomes:

gzip -r test

test/
   -- fileone.csv.gz
   -- filetwo.csv.gz
   nestedtestdir/
      -- nsfilefileone.xlsx.gz
      -- hello.txt.gz

As you see, it recursively goes to each file inside the folder and compresses that file, saving it with a .gz extension.

Note: It modifies all the original files inside that folder and also other folders inside the given folder. In case you don’t want to modify the original files, add -k to keep the original files inside a directory like this:

gzip -r <your-directory> -k

To compress a directory using gzip without compressing files inside it, the hack would be to use tar and pass the tar file to be gzipped.

tar zcvf <your-gzip-file-name>.tar.gz <dir-name-to-be-gzip>/

Here, zcvf stands for z -> compress archive with, c -> create, v -> verbose, f -> filename.

You can achieve the same by:

tar -cvf - your-dir-name | gzip > your-dir-name.tar.gz

Here, -cvf stands for compress, verbose, filename after hyphen (-) your directory name. The | (pipe) symbol is used to pass on the result from one command to another command, then gzip is used to compress, and > (greater than) symbol denotes writing into your-dir-name.tar.gz, the target/output file name with .gz extension.

That’s it. Thanks for reading! Feedback is always welcome. Happy times !!!

Introduction to Machine Learning

Hello All , It’s been long time i haven’t written anything in my blog. I have just now started learning “Machine Learning” . I will try to write a post about my learning as much as possible .

Why I choose Machine Learning?

Machine Learning came some long time ago , why i choose to learn now? The Information technology world is changing every single day . Yes “Change is the only thing constant” in this technology world .

Even though i have started my career as software developer , it was in my long term list to learn machine learning , i didn’t pay much attention to it . Now i have decided to learn out of my passion and interest for it .

How am i learning Machine Learning?

I am learning Machine Learning from videos and text books . I haven’t taken any course for that . I have started watching Andrew N videos and few texts from others to learn .

What is Machine Learning?

It’s very difficult to explain in words , i will try to explain in my own words

Machine Learning defines ability to teach/train machine(system) to predict certain things based on the rules given to them and also improves efficiency based on the experience .

Best real time example is “Playing chess against computer AI” . In AI it has rules( how pieces can move , how many steps can move) , with that it predicts and makes a move for a human move. In short there is no hard coded way if this move then this move , It calculates all possible moves against a move and makes the best move . How this is been done? System is loaded with tactics and statistics for a game . It improves from it’s experience and becomes better at it .

Let’s get to the introduction of what we are going to see in this .

We can divide the Machine Learning into four important Parts

Supervised Learning
Unsupervised Learning
Deep Learning
Reinforcement Learning

We will see each one with small introduction to it , in later posts we will explain each one with detailed examples .

Supervised Learning

In a given data (known labels) find meaningful relationship between them and predict/estimate the output. We can split Supervised into two categories

Regression
Classification

Regression:

For example: Predicting House Price for a given square feet .

Lets assume this data set 1000sqft -> 4Lakhs, 2000 -> 7.5 lakhs , 5000sqft -> 18lakhs .

When asked to find the price for 700Square feet , we can easily draw and map the price from given data set . This is called regression , because the value we are trying to predict is continuous.

Classification :

This another type of supervised algorithms . Best example for this type is predicting /identifying blood group of humans .

Here Y axis value is constant ( O+, O-, A+, A-, B+, B-, AB+, AB-) . But we can have discrete number of x values (Human blood samples) . Here Y can take discrete values of X hence it’s called classification Supervised Learning .

Unsupervised Learning:

Unsupervised learning defines , analyses unlabeled data and groups/clusters them .

for example:

In above image , as you can see given unlabeled data , unsupervised machine learning algorithms analyzes and finds pattern and groups/clusters them together . This is called Unsupervised learning where unknown data given .

We will see about other two types also in detail once we finish these types of learning in detail in upcoming posts.

That’s it . Thanks for reading . All kind of feedback are welcome. Happy coding !

Dictionary in Python3

Hi all . Today we are gonna see dictionary in python3.

In python2.7
d= {"a": "b", "b": "c", "c": "d", "d": "e", "e": "f"}

d.keys() —> [‘a’, ‘c’, ‘b’, ‘e’, ‘d’]

d.values() —> [‘b’, ‘d’, ‘c’, ‘f’, ‘e’]

Here d.keys() returns list of keys, d.values() returns list of values respectively.

In Python3 . These functions return dictkeys and dict values
d= {"a": "b", "b": "c", "c": "d", "d": "e", "e": "f"} d.keys() ---> dict_keys(['d', 'c', 'b', 'e', 'a']) d.values() ---> dict_values(['e', 'd', 'c', 'f', 'b'])

However if we want same functionality as 2.7 we can get like this
list(d.keys()) ---> ['d', 'c', 'b', 'e', 'a'] list(d.values()) ---> ['e', 'd', 'c', 'f', 'b']

There is no dict.iteritems(), d.has_key() function in python3
d.items() ---> dict_items([('d', 'e'), ('c', 'd'), ('b', 'c'), ('e', 'f'), ('a', 'b')]) list(d.items()) ---> [('d', 'e'), ('c', 'd'), ('b', 'c'), ('e', 'f'), ('a', 'b')]

Instead has_key() function we can check like this
'a' in d.keys() --> True 'z' in d.keys() --> False

If key doesn’t exists it will return false.

d.pop(‘a’) –> pop item from dict by key

d.popitem() –> pops most recently inserted item in dict

d.clear() –> clears entire dictionary

d.setdefault(‘z’, 10) –> sets default value for ‘z’ to 10

d.get(‘z’) –> 10 # gets value of key ‘z’, returns none if key doesn’t exist.

How to get video files duration and resolution in python

Hi all,

Today i was about to find video file duration and resolution and few more info in python.

In debain based systems type this command in terminal

avconv

If this shows version , like this

avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav developers
built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
Hyper fast Audio and Video encoder
usage: avconv [options] [[infile options] -i infile]… {[outfile options] outfile}…

Use -h to get full help or, even better, run ‘man avconv’

If it says commond or package not found, then install this by

sudo apt-get install libav-tools

After successful installation, In terminal

avconv -i "filepath"  # give path to your video file

You will see output like this
Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: mp42mp41
    creation_time   : 2015-10-21 16:41:08
Duration: 00:00:30.00, start: 0.000000, bitrate: 748 kb/s
    Stream #0.0(eng): Video: h264 (Constrained Baseline), yuv420p, 480×240, 488 kb/s, 25 fps, 25 tbr, 25 tbn
    Metadata:
      creation_time   : 2015-10-21 16:41:08
    Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, fltp, 255 kb/s
    Metadata:
      creation_time   : 2015-10-21 16:41:08

You can see the resolution and duration highlighted my result.

Now lets see how to use this in python to get video resolution, duration.

The idea is simple , am gonna use subprocess and pipe the output

Here is the python code.


from subprocess import Popen, PIPE
import re

def getvideodetails(filepath):
    cmd = "avconv -i %s" % filepath
    p = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE)
    di = p.communicate()
    for line in di:
        if line.rfind("Duration") > 0:
            duration = re.findall("Duration: (\d+:\d+:[\d.]+)", line)[0]
        if line.rfind("Video") > 0:
            resolution = re.findall("(\d+x\d+)", line)[0]
    return duration,resolution

# call function with file path
getvideodetails("filepath")

This code can be found in gist too here

Thats it.

Happy coding!!!
Happy times !!!

MongoDB Basics

Hi all. Today we are going to see about mongodb basics.

what is it?

Mongodb is a No-Sql Database , document based database (closely dictionary in python , ruby). Here you can read about it official documentation .

why is it used for?

It’s used when you no need to care about your schema . It means when you are using mysql , we have to have ID field integer, name varchar . Here it’s not needed .

Installation:

open terminal (cntl+alt + T)

sudo apt-key adv –keyserver hkp://keyserver.ubuntu.com:80 –recv 7F0CEB10

sudo apt-get update

sudo apt-get install -y mongodb-org

Hope you have successfully installed mongo in your system.

if you’re having trouble see official site for trouble shooting here

Time to play with it :

type mongo and enter in your shell

you will see something like this

MongoDB shell version: 2.4.9
connecting to: test

To see all database:

show dbs

it lists all databases. This is equal to show databases in MYSQL

To select a particular database

use databasename

To see all collections inside a database.

Note: In mongodb collections refers tables. we won’t call them as tables . It’s collections here.

show collections

this is equals to show tables in MYSQL

Let’s create a database called bala .

use bala

unlike MYSQL it won’t throw you error unknown database.

to check in which db you’re issue db command in mongo shell.

it shows bala

now create a document in it.

db.mycollection.insert({“name”: “bala”})

what i did here?

db => bala

mycollection => our collection name

insert => operation name

{“name”: “bala”} => data we are inserting into our collection

To see a document is inserted into our db , type this command

> db.mycollection.find()
{ “_id” : ObjectId(“55a6070cab3e0cf5c31434cf”), “name” : “bala” }
>

see our document is inserted, find returns all documents in a collection(table) .

Have you noticed _id in above output. Yes that’s automatically created by mongo . Its alpha numeric . Similar to id primary key in MYSQL.

To see one document in a collection

> db.mycollection.findOne()
{ “_id” : ObjectId(“55a6070cab3e0cf5c31434cf”), “name” : “bala” }
>

Now try inserting other document

db.mycollection.insert({“name”: “hari”, “country”: “india”, “state”: “Haryana”, “age”: 20})

what we did ?

we gave country , state, haryana . so many keys . what happened?

As i said it’s schema less database , it doesn’t care about schema.

now let’s go and check it out.

> db.mycollection.find()
{ “_id” : ObjectId(“55a6070cab3e0cf5c31434cf”), “name” : “bala” }
{ “_id” : ObjectId(“55a60976ab3e0cf5c31434d0”), “name” : “hari”, “country” : “india”, “state” : “Haryana”, “age” : 20 }
>

see it shows two documents in our collection. how cool is this .

To find a document by condition (by name , age or any field)

let’s see i want to see all document’s which have name “hari”

> db.mycollection.find({“name”: “hari”})
{ “_id” : ObjectId(“55a60976ab3e0cf5c31434d0”), “name” : “hari”, “country” : “india”, “state” : “Haryana”, “age” : 20 }
>

here i have only one document having name “hari”, if I ‘ve many then it will show all documents.

We can see particular field value also by condition

let’s say i want to see all names alone in my collection

> db.mycollection.find({}, {“name”:1})
{ “_id” : ObjectId(“55a6070cab3e0cf5c31434cf”), “name” : “bala” }
{ “_id” : ObjectId(“55a60976ab3e0cf5c31434d0”), “name” : “hari” }
>

{} => empty dict to select all documents

“name”:1 => select only name from all documents

we can select as many documents as possible

fieldname: 1 => selects the field to result.

fieldname:0 => ignores the filed to result.

Here instead of { } , we can give condition also .

Try it out those commands also.

Let’s update a document named “bala” , adding age field into it

> db.mycollection.update({“name”: “bala”}, {$set : {“age”: 20}})

$set is used to update field

let’s see it’s updated or not.

> db.mycollection.find({“name”: “bala”})
{ “_id” : ObjectId(“55a6070cab3e0cf5c31434cf”), “age” : 20, “name” : “bala” }
>

its updated , age field added into it. if we have many documents named “bala” then all got updated by above command.

till now we seen creation,insertion, updation.

Let’s move on to deletion of a document

To delete a document in collection

> db.mycollection.remove({“name”: “bala”})
> db.mycollection.find({“name”: “bala”})
>

first command deleted the document, second one verifies that we don’t have document name “bala”.

To remove all documents in a collection

db.mycollection.remove()

This command removes all document in a collection.

That’s all about mongodb basic (curd operations) . Try playing with that , we will see with advanced commands or integration with any language (python or ruby) later .

Thanks for reading . Happy hacking .

String Module In Python3

Hi all. After long time I’m writing a post . Finally started learning python internals and playing with c python source code little bit.

Its actually nice to read the source code of cpython . To get a copy of source code follow this Cpython .

Hope you have a running copy of cpython. Inside the source code directory run ./python

i have version 3.5.0a0 like this

Python 3.5.0a0 (default:5754f069b123, Dec 13 2014, 00:41:29)
[GCC 4.8.2] on linux
Type “help”, “copyright”, “credits” or “license” for more information.
>>>

Here I’m not going to talk about python3 . Since i started coding and slowly moving to python3 from python2 (will explain module by module).

Lets start using string module. inside shell

import string

s = “this is my test string ”

print(string.capwords(s))

This Is My Test String

It just capitalize the first letter in every word in a given input string. The actual source code for capwords is

def capwords(s, sep=None):
return (sep or ‘ ‘).join(x.capitalize() for x in s.split(sep))

you can check in file cpython/Lib/string.py

It just splits the words and capitalize and joins for result.

If you didn’t download source code . checking in ipython or bpython or python shell means . Don’t worry there is a another option to see the source code . Not only this module all the modules source code you can see .

Lets see that .

import inspect

inspect.getsource(string.capwords)

‘def capwords(s, sep=None):\n “””capwords(s [,sep]) -> string\n\n Split the argument into words using split, capitalize each\n word using capitalize, and join the capitalized words using\n join. If the optional second argument sep is absent or None,\n runs of whitespace characters are replaced by a single space\n and leading and trailing whitespace are removed, otherwise\n sep is used to split and join the words.\n\n “””\n return (sep or \’ \’).join(x.capitalize() for x in s.split(sep))\n’

See it returns source code in a string . How cool this inspect module ??. It has so many useful functions use it .

now coming back to our string module

string.ascii_letters

‘abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ’

string.ascii_lowercase

‘abcdefghijklmnopqrstuvwxyz’

string.ascii_uppercase

‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’

I used to replace strings like this

k = “this is a test replace with b”

k.replace(‘a’,’b’)

I found this is less efficient than this one

test = str.maketrans(‘a’,’b’)

print(k.translate(test))

‘this is b test replbce with b’

Both functions does the same job but maketrans done in efficient way . It just creates mapping table and translates .

I test with time-it. Second one takes less time than first one .

%timeit k.replace(‘a’,’b’)
10000000 loops, best of 3: 167 ns per loop

%timeit k.translate(test)
10000000 loops, best of 3: 143 ns per loop

if you have noticed something above, i used str.maketrans(from,to)

In case of python 2.7+ to 3.

you can use like this

test = string.maketrans(‘a’,’b’)

print k.translate(test)

In python3.1maketrans () is not a function of string module

Because in Python3 Strings are not bytes . Strings are Unicodes.

In python2 bytes was an alias for str.

You can check this in your shell

bytes is str (In python2.7 shell)

True

bytes is str (In python3.5.0a0)

False

Hope you got something . Happy coding . Thanks for reading . Feel free to tell your suggestions .

Nginx to serve static files example

Hi all .. Today we ll see how to use nginx to serve static files .

what is Nginx?

Niginx is a high performence web server software. Its more flexible and lightweight than apache. Niginx is a reverse proxy protocol.

wait a minute.. what is meant by reverse proxy ?

lets say x- a client and y – a server

x->y

x sends request to server [this is direct proxy]

in reverse proxy

x sends request to server but request is sent to some internal proxy and that proxy passes request to server and sends response from server to the client. The client may not be aware of this.

In short, requests are not directly processed by server some intermediate guy will process requests and responses.

x->z->y [here z is that intermediate guy]

Got something ??

Lets see the installation of nginx

1. open Terminal (cntrl + alt +T)

2. sudo apt-get install nginx

Lets play with nginx now .

To play ,lets create one directory

mkdir /cache

cd /cache/

chmod 777 /cache/

lets create some dummy files in this directory

cat >>hi.txt

hi this is test file

this is line

cntrl + d [press contrl + d to save this file]

cat >> second.txt

this is my second file

this is testing second file

press contrl + d to save this file .

Now ,its time create a sample configuration file to server this directory.

Before we write ,its useful to know about two import directory in nginx

1. sites-enabled

cd /etc/nginx/sites-enabled/

This directory contains symlink files from sites-available directory

[we can create files here but don’t do that it’s not a good way to do]

2. sites-available

cd /etc/nginx/sites-available/

here all the config files are there for nginx

make sure your inside sites-available directory else

do cd /etc/nginx/sites-available/

touch sample.conf

open this sample.conf in your favorite editor and type the below code

server {
    listen                *:9000;
    server_name          _;
    access_log            /var/log/sample.access.log; # this line is optional for log purpose
    error_log             /var/log/sample.error.log; # this line is optional

    location /test/ {
        alias /cache/;
        autoindex on;
        expires off;
        default_type application/octet-stream;
   }
}

Lets see ,

listen *:9000 –> server listens to the port 9000

server name – is optinal [you can give your domain name like http://www.example.com,]

next two lines are to log who accesses files and error details

next loctaion /test/{

telling nginx -x to server this location

alias /cache/ —> /cache directory can be accessed using /test/

auto index on —> to list all the files inside directory [ not recommended ,because user will know all the files inside your directory ]

expires off [ this disables caching files ]

default_type application/octet-stream –> this sets ,whenever the user visits this page it serves the content of the file .[asks for open or download]. It never opens in browser

if you want to just view in browser not to download

just comment that last line which contains octet-stream

just save this file now

now lets create a symlink to sites-enable

It will be like this

sudo ln -s /etc/nginx/sites-available/sample.conf /etc/nginx/sites-enabled/

Note: Always use absolute path . don’t use relative path like this sudo ln -s sample.conf /etc/nginx/sites-enabled/ — this will not work . Always use absolute path

ok lets restart nginx server

sudo service nginx restart

open your favorite browser and visit localhost:9000/test/

you will see like this

click on the any file [ note i commented octet-stream]

if you want file to be downloaded uncomment that last line . You browser will ask file to be opened or download

Thats it … Play with it .. Happy coding..:)

Start Using TMUX

Hi …all ,till few days ago I used screen in remote server . Now i switched to TMUX from screen. It has so many advantages and features as compared to screen .

what is Tmux?

Tmux is a software application that multiples several virtual consoles ,that allows us to use multiple terminal session into single terminal window.

Installation

apt-get install tmux

Lets start using and play with tmux

To start new session open terminal and type

tmux

To attach to a session

tmux attach-session -t [session name]

To split the window into panes (two terminal session in same window )

cntrl+b % (splits vertically)

cntrl+b ” (splits window horizontally)

To move from one pane to another pane

cntrl +b o

To open new window

cntrl +b c

To go to next window

cntrl +b n

To go to previous window

cntrl +b p

To kill current pane or window

cntrl + b x

To close all other pane expect current

cntrl + b !

To exit from shell

cntrl + b d

To list windows

cntrl +b w

To go to particular window(lets say #)

cntrl +b #

To go to last active window

cntrl +b l

To list all the sessions

tmux list-sessions

To rename current window

cntrl +b ,

This is how i’m using tmux in my remote server .. In single window i’m using three terminals in it . see the screen shot below..

Here i’m using three terminal session in single window .

In first pane – i’m running ipython

In second pane – i’m running glances

In third pane – mysql shell

commands i used for these to achieve are:

tmux – to start new tmux session

cntl +b % – split vertically

cntrl +b “ -split 1st pane into by horizontally

cntrl + b o –to switch between panes

See how useful these tool .. Start using this and play with it ..

Thanks for reading .. Please feel free to tell your suggestions ..

Happy coding .!!!!

Hello World in Django !!!!

Hi …After long time i ‘m blogging about django..Lets start our journey to django .Before reading this i would suggest to get some knowledge in python .

My suggestions for python learning are

A byte of python with pdf
Dive into Python
Learn python the Hard way

What is Django?

Django is a Web framework written in python language .

what is meant by frame work?

After searching about framework, Frameworks are similar to libraries or templates that are already written for you, you can re-use the code to build your system . i.e(Collection of codes that uses some control mechanisum).

still didn’t get???

I explain with my view, lets forget about all technical terms and others. Lets say you want to build your new house ?

To build new house what are the things you needed?

money
stones
cement
empty ground (place)
water
sand and others stuffs etc….

now same thing for building your system(project)

Framework offers everything you needed, the only thing you need to do is ,place the things in correct manner. like(database details in proper place, your logics , representation of your data. etc.)

Hope you understand something !!!!

now coming to our django framework.It follows MVC pattern like Ruby on Rails .

MVC: => Model View Controller

Model: for Database access.(this contains database,table details)

Views: your logic goes here

Templates: To represent your data(html files)

Why MVC or What is the Advantage of this?

The biggest Advantage of MVC is ,one’s change doesn’t affect other.

for example if you want to change your database details(say db name or table details) you need to change in model file only( no need of find and replace in entire project).Because each and everything are loosely coupled(independent). Same thing applies for view and templates too.

didn’t get it??

while doing sample code i will explain it …

To install django see install

Sorry i ‘m not going to tell about installation . Since i’m an linux user I know about installation in linux only. You can find lot of source for your operating system installations.

Django documentation is fair enough for any os.

After installing ,lets create the sample project.

Its good practice to create working directory for learning any language .

open terminal(cntrl+alt+T)

create directory mkdir djcodes(here djcodes is my directory name ,you can give any name)

cd djcodes(change to working directory)

To start a new django project (i’m using django 1.5 version):

django-admin startproject sample # here sample is a project name

change directory to sample

cd sample/

now issue ls command ,

manage.py sample

You have manage.py file and sample folder inside sample project .

manage.py – points to the settings file in your project. (This files are automatically created by django)

Inside sample folder you have 4 files

__init__py – this will indicate your project as python package to compiler.

urls.py – file to hold the urls of your website .(e.x)http://localhost/hello

here in order to use /hello in our project you have to mention this in urls.py.

(see my below explanation for these concepts)

settings.py – File that will hold all apps,database settings of your information .

(if you open this file means you can see,time zone,templates etc..). You will learn more about these files in my upcoming posts.

Wsgi.py– This file handles our requests and responses .(our django development server)

Ok. Lets start the server by

./manage.py runserver (Note inside project directory)

this is show like this

Validating models…

0 errors found
Django version 1.4.5, using settings ‘sample.settings’
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
[17/Jan/2014 11:45:00] “GET / HTTP/1.1” 200 1957

Open your favorite browser and see the link http://127.0.0.1:8000/

It worked!

Congratulations on your first Django-powered page.

Of course, you haven’t actually done any work yet. Here’s what to do next:

If you plan to use a database, edit the DATABASES setting in sample/settings.py.
Start your first app by running python manage.py startapp [appname].

You’re seeing this message because you have DEBUG = True in your Django settings file and you haven’t configured any URLs. Get to work!

This is default page in django .

Our goal is Hello world page in django .

Lets Start creating our app and display hello world

To create an app(inside project directory)

django-admin startapp hello

This will create a hello folder in project directory.It has four files

__init__.py – this file indicates your app as python package.

models.py – file to hold your database informations

views.py – your functions to hold requests,logics etc.

tests.py – for testing purposes.

Three things to do for our task

1. add url in urls.py with associate function.

2. write code for url in urls.py

3. html file to render a response.

Lets add url in urls.py

gedit /sample/urls.py

add your like this

from django.conf.urls import patterns, include, url
from hello.views import myfunction

# Uncomment the next two lines to enable the admin:
# from django.contrib import admin
# admin.autodiscover()

urlpatterns = patterns('',
    # Examples:
    # url(r'^$', 'sample.views.home', name='home'),
    # url(r'^sample/', include('sample.foo.urls')),

    # Uncomment the admin/doc line below to enable admin documentation:
    # url(r'^admin/doc/', include('django.contrib.admindocs.urls')),

    # Uncomment the next line to enable the admin:
    # url(r'^admin/', include(admin.site.urls)),
    url(r'hello/$',myfunction),
)

my views.py(In hello/views.py)

# Create your views here.
from django.http import HttpResponse
def myfunction(request,):
	return HttpResponse("Hello")

save your files .
now run server ./manage.py runserver

Now see in browser by typing http://localhost:8000/hello

this will return hello in page . Thats it our goal is done .

What happens behind the scene . I will explain shortly.

when you type localhost:8000/hello —> this will send request to django

this is will read urls.py and look for pattern and url match . if it matches it calls the associated function.

In our case it matches hello in urls.py and calls myfunction in views.py.

In views.py –> we have the code to display the hello as HttpResponse .

Thats it .. Thanks for reading… Happy coding !!!