How to create ascii art using VIM plugin DrawIT

Installing VIM plugin DrawIT

Install the plugin if it is no available in your machine

This script/plugin is distributed as a vimball

This can be downloaded here

To download source go to /usr/local/src Create a directory VIM. go to the directory /usr/local/src/VIM (NOTE: it isn’t manadetory to keep source in this location, it’s upto you)

Dowload the source with following wget

wget http://www.vim.org/scripts/download_script.php?src_id=21108 -O DrawIt.vba.gz

To install follow the instructions

Open file vim DrawIT.vba.gz In command mode enter :so %

quit :q

Quick start with DrawIt

That’s all you have to do to install a plug in. Now to test, open a new file

and type the following in command mode

\di

If you see [DrawIt], the plugin is enabled an you can draw you art.

Here is how you will start and stop DrawIt

\di start DrawIt \ds stop DrawIt

User your arrow keys to draw whatever you want

To get help on drawit and to find handy key to draw, type the following in command mode in VIM :help drawit.

 

 

 

How to implement PayPal payment gateway

The PayPal REST APIs are supported in two environments. Use the Sandbox environment for testing purposes, then move to the live environment for production processing.

The following endpoints address are two environments:

A complete REST operation is formed by combining an HTTP method with the full URI to the resource you’re addressing. For example, here is the operation to create a new payment:

The PayPal REST sdk can be obtained through pip

OAuth Request / Response

Client Id and Secret Id can be obtained from the application created in the paypal account.

For the following each API call, you’ll need to set request headers, including the access token.

Creating a WebProfile:

name:

The name of the web experience profile which should be unique among the profiles for a given merchant.

presentation:

It contains the parameters for style and presentation.

input_fields:

Parameters for input fields customization:

  1. allow_note : It enables the buyer to enter a note to the merchant on the paypal page during checkout.

  2. no_shipping : Determines whether or not PayPal displays shipping address fields on the experience pages.

    • 0 – PayPal displays the shipping address on the PayPal pages.
    • 1 – PayPal does not display shipping address fields whatsoever.
    • 2 – If you do not pass the shipping address, PayPal obtains it from the buyer’s account profile.
  3. address_override : Determines if the PayPal pages should display the shipping address supplied in this call, rather than the shipping address on file with PayPal for this buyer.

    • 0 – PayPal pages should display the address on file
    • 1 – PayPal pages should display the addresses supplied in this call instead of the address from the buyer’s PayPal account.
flow_config:

Parameters for flow configuration

  1. landing_page_type : Type of PayPal page to be displayed when a user lands on the PayPal site for checkout.

    • Billing – The Non-PayPal account landing page is used
    • Login – The paypal account login page is used.

Creating a Payment:


 

intent:

Payment intent. Allowed values are:

  • “sale” – For immediate payment
  • “authorize” – To authorize a payment for capture later
  • “order” – To create an order
experience_profile_id:

Id that will be obtained from the response of web profile request

payer:

Source of the funds for this payment represented by a PayPal account or a credit card.

  • payment_method : Payment method used. Must be either credit_card or paypal.
  • funding_instruments : A list of funding instruments for the current payment
  • payer_info : Information related to the payer
  • status : Status of the payer’s PayPal account. VERIFIED or UNVERIFIED
transactions:

Transactional details including the amount and item details.

redirect_urls:

Set of redirect URLs you provide only for PayPal-based payments.

  • return_url : The payer is redirected to this URL after approving the payment.
  • cancel_url : The payer is redirected to this URL after canceling the payment.

Execute an approved PayPal payment:

Use this call to complete a PayPal payment that has been approved by the payer.

The payment_id and payer_id are passed in the return_url. Once the payment is executed,it returns an array of payment object.

In the response state of the payment is obtained as : created approved failed, canceled, expired or pending.

The transaction details in the response contains state of the sale which is obtained as: pending, completed, refunded or partially_refunded

If the payment state is approved and the sale state is completed, the payment is successfully executed.

How to chat securely using Pidgin and OTR

These days surveillance news are coming out frequently. After Snowden’s revelation if you’r suffering from paranoia and want to secure your digital presence, follow this tutorial to communicate securely.

  1. Install Pidgin chat client.
    • for ubuntu –
    • for arch linux –
    • also you can download it manually from here & then install it as per instructions
  2. Install OTR plugin of Pidgin.
    • for ubuntu –
    • for arch linux –
  3. Now start Pidgin. It will show ‘Accounts’ Popup. Click on ‘Add’ button. add
  4. Now you will get ‘Add Account’ popup.
    add-account-0
  5. Now configure new account as follows.
    • Tab ‘Basic’
      • Login Options
        • Protocol : XMPP (don’t use ‘Facebook XMPP’)
        • Username: (don’t use a username which will somehow connected to real you)
        • jabber.rayservers.com
        • leave blank
        • enter password you want
      • User Options
        • Local alias : Leave blank
        • New mail notifications : DO NOT check
        • Use this buddy icon : check if you want
        • Create this new account on the server : MUST checkadd-account-1
    • Tab ‘Advanced’
      • Connection security : Require Encryption
      • Allow plaintext auth over unencrypted streams : DO NOT check
      • Connect port : 5222
      • Show Custom Smileys : check
      • Create this new account on the server : MUST check add-account-2
    • Tab ‘Proxy’
      • Proxy type : Use Global Proxy Settings
      • Create this new account on the server : MUST check add-account-3
    • Tab ‘Voice and Video’
      • Use silence suppression : leave default
      • Create this new account on the server : MUST check add-account-4
  6. Now to add this new account, click on ‘Add’
  7. Wait for few seconds. Popup will come for ‘SSL Certificate Verification’. Click on ‘Accept’. Cross-check ‘Certificate Information’. Then ‘Accept’ cetificate. cert-1 cert-2
  8. Now you will get popup saying ‘Register New XMPP Account’. Click on ‘Register’.
  9. From top menus select
    Tools -> Plugins -> Off-The-Record Messaging (MUST checked)
  10. Click on ‘Configure Plugin’
  11. Configure ‘Off-the-record Messaging’ popup as follows, otr-1
    • My Private Keys –
      • Click on ‘Generate’ if you get message ‘No key present’. Generating keys takes time. When keys are getting generated try to do some CPU intensive work to add more entropy.
    • Default OTR Settings – Check all
      • Enable private messaging – check
      • Automatically initiate private messaging – check
      • Require private messaging – check
      • Don’t log OTR conversations – check
    • OTR UI Options
      • Show OTR button in toolbar – check
  12. Once key is generated, click on ‘Close’ to close popup windows of ‘Off-the-record Messaging’ & ‘Configure plugin’.
    otr-2
  13. Now in top window ‘Buddy List’ ,
    Tools -> Preferences -> Logging -> Do NOT check any options here & close popup. otr-4
  14. Now enable your new account as,
    Accounts -> Enable account -> Select newly created account
  15. Now to add buddy,
    Buddies -> Add buddy
  16. In ‘Add Buddy’ popup, enter ‘Buddy’s username’ – something like ‘foo@bar.qux.com’.  Optionally you can add ‘Alias name’ for ease. Here important thing to remember is, once you add buddy it will appear in your buddy list only after authorization of your buddy.
  17. Now if you add buddy successfully and he is online & double-click on buddy and start to chat.
  18. Here you will get another private messaging window. Don’t forget to ‘Start OTR’ here & to Authenticate your buddy.
  19. Further, you can use Tor with Pidgin to circumvent IP address.

How to blink browser tab

Have you ever wished to blink browser tab on certain activity to get user’s attention?

Here is a scenario: Suppose there is a chat application installed on your website. Now what if the user of your website has multiple tabs opened in his browser and there is an incoming message in your website? How will you make your user realize that there is an unread message? Of course you can play some music, but it has some limitations. For instance, user may be listening to some songs or speakers could be muted. If none of them is applicable then also he has to go through each and every single tab in his browser and find out the one which is playing that music.

Visual blinking is the best way to get user’s attention and the easiest way to achieve that is to keep blinking the title of your website until user returns.

Here’s a JavaScript function to do so:

Just execute the function like below and browser tab will start blinking:

How to measure the duration of a function call or code block in python

The simple way to measure the duration of function call in python using context management.

Some times we may encounter the situation where we need to know total time taken by the function call. Here is the code which is pretty much handy and simple to measure the duration of function call  or  time taken by the function(call) in python

Here is how you apply the above code to get the time taken by the function call


 

Output would look like as follows,


 

How to implement social Login for Django app

In this article we will get to know about how to login to your django app by using social logins like Facebook and Google.

Start a simple Django project


 

Running ./manage.py syncdb and then ./manage.py runserver and navigating to localhost:8000 will show the familiar “It worked!” Django page. Let’s put some custom application code in place, so that we can tell whether the current user is authenticated or anonymous.

Show current user’s authentication status

Now, the very small customizations we’ll add are:

Relevant portion of settings.py:


 

Template: thirdauth/base.html:

Template: thirdauth/home.html:

File views.py:


 

File urls.py:


 

Install Python Social Auth

Second, let’s make some modifications to our settings.py to include python-social-auth in our project:


 

Lets update the urls module to include the new group of URLs:


 

And finally, let’s update the database models:

./manage.py syncdb

Add links for logging in and logging out.

Since we’ll be logging in and out multiple times, let’s include django.contrib.auth URLs into our URLs configuration:


 

Let’s modify our Home page template like this:

For the login and logout links in this template to work correctly, we need to modify a few things. First, let’s take care of logout, it’s easier. Just add ‘request’ to the context object that we pass into template-rendering code.

Updated views.py:


 

For login to work, let’s first add a LOGIN_REDIRECT_URL parameter to settings (to prevent the default /account/profile from raising a 404):

LOGIN_REDIRECT_URL = ‘/’

Get Client IDs for the social sites.

For All the social networks we are using in this demo, the process of obtaining an OAuth2 client ID (also known as application ID) is pretty similar. All of them will require that your application has a “real” URL – that is, not http://127.0.0.1 or http://localhost. You can add an entry in your /etc/hosts file that maps 127.0.0.1 to something like “test1.com”, and the URL of your application becomes http://test1.com:8000 – that is good enough for testing. You can change it in the social app settings when it goes into production.

Facebook:

Google:

 

How To Mount S3 Bucket In Linux Using S3FS

Here is the simple step by step procedure to mount s3  bucket on linux

Step 1: Remove Existing Packages


 

Step 2: Install Required Packages


 

Step 3: Download and Compile Latest Fuse


 

Step 4: Download and Compile Latest S3FS


 

Step 5: Setup Access Key


 

 

To unmount


 

 

How to secure yourself with GPG

Generate your key


  1. Run following command in your shell,
  2. Now program will ask you to choose couple of options, use following preferences
  3.  Please select what kind of key you want: 1    RSA and RSA (default)
  4.  What keysize do you want? (2048) 4096
  5.  Key is valid for? (0) 0
  6. Is this correct? (y/N) y
  7. Now enter name, email and comment message.
  8. Change (N)ame, (C)omment, (E)-mail or (O)kay/(Q)uit? o
  9. Finally, enter a passphrase to protect your secret key.

Edit your key


We can later edit key to use other options.
e.g Lets set our key to use stronger hashes.

  1. Edit key using following command,
  2. Now set hash preferences as follows,
  3.  Really update the preferences? (y/N) y
  4. Enter your passphrase
  5. Save new preferences by command,

Make available your key


There are 2 ways to make available your key to other users.

  1. Give them manually. Use following command,

    You will get your public key. Copy and paste it and send to other user.
  2. Upload to key server. You can do this again using 2 ways. One is using, forms available on server. While for second way, first grab your id using following command’s output & then upload to keyservers like http://pgp.mit.edu/

 

Importing other keys


  1. Import other user’s keys. We can import keys of other users with multiple ways. From text file – If someone sends you text file containing his public key, import it as,

    From key server – There are some popular key serves which host public keys.
    One of such server is http://pgp.mit.edu. Here you can search particular user’s key as follows,
  2. Validate key. The easy way to validate person’s identification is match fingerprint of key.
  3. Sign imported key as,
  4. Optionally you can send back signed key

Using gpg key


  • To encrypt message using your key use following command,
  • To decrypt file,

    Creating revocation certificate

There is always possibility that your master key-pair may get lost. (and may be stolen if you are unfortunate). If this happen, you must tell other people to not use your public key. This can be done using revocation certificate. Generate revocation certificate using following command,

Store it safe somewhere separately from master key-pair

Some useful commands


  • List available keys,
  • Update key information,

     

 

 

Coloring shell output

Using coloring, we can enhance output of shell script. Run following script in your terminal and see magic.

 

How to implement Websocket server using Twisted.

HTTP is a request-response type one way protocol. For the web application where continuous data is to be send, websocket was introduced. Unlike HTTP, websocket provides full duplex communication. Websocket, which can be said as an upgraded version of HTTP, is standardized to be used over TCP like HTTP. In this article I will share my experience in implementing websocket with twisted, a framework of python for internet. If you are familiar with websocket, then you can skip to twisted.web or else below is a little introduction to websocket.

WebSocket

To initiate communication using websocket, a Handshake need to be done between client and server. This procedure is backward compatible to HTTP’s request – response structure. First the client sends a handshake request to the server which looks like:

Sending Upgrade header in request with value websocket will acknowledge server about websocket communication. Now if server supports websocket with specified sub-protocols (Sec-WebSocket-Protocol) and version (Sec-WebSocket-Version), it will send adequate response . Possible response could be:

In response, server will send 101 Switching Protocols code and Sec-WebSocket-Accept whose value is calculated using Sec-WebSocket-Key. you can find more information here. After a successful handshake, any of the peer can send data to each other which must be encoded in binary format described in websocket RFC. A high-level overview of the framing is given in the following figure.

Twisted.web

websocket using twisted wire diagramAs in normal twisted.web server , at TCP level, we have HTTPChannel class (a child class of T.I.protocol.Protocol) and server.Site class (which is the child class of T.I.protocol.ServerFactory). Also a Resource instance needs to be passed to server.site class, so that it can serve GET request.

Whenever a data is received, DataReceived method of HTTPChannel is invoked. Now if data starts with ‘GET’, allow the HTTPChannel handle it, which will invoke the render function of the root resource provided to Site class. Render will set 101 response code and will compute the websocket response key. During handshake do not send any raw data, because if handshake is successful this will be considered as framed binary data. Even if you want to send, frame it and send.

If data doesn’t start with ‘GET’, that means we can assume it is a binary encoded message. Now this message can be decoded using Frame.py, which is a very simple data framing module following WebSocket specification. Data send to the client by server should be unmasked as per the websocket specification.

Below is code example of an echo websocket server.