Use different Python version with virtualenv

virtualenv -p /usr/bin/python2.6 /provide/path/to/new/virtualenv/

Where python2.6 is the python version which can be changed to anything and virtualenv path is the folder created by you to install virtualenv in it

mysql retrieve first 100 characters

 

SELECT LEFT(field, 100) AS excerpt FROM table(s) WHERE ...

See the LEFT() function

 

Calculate n-gram in python

def ngrams(sequence, n, pad_left=False, pad_right=False, pad_symbol=None): 
	if pad_left: 
		sequence = chain((pad_symbol,) * (n-1), sequence) 
	if pad_right: 
		sequence = chain(sequence, (pad_symbol,) * (n-1)) 
	sequence = list(sequence)     
    count = max(0, len(sequence) - n + 1) 
    return [tuple(sequence[i:i+n]) for i in range(count)] 

Now lets get Started:

1) Bigrams:
sequence = [1,2,3,4,5]
n=2
ngrams(sequence,n)
[(1,2),(2,3),(3,4),(4,5)]

For Trigrams n=3 and so on..
If you want a left or right padding when the numbers are odd then mention the left Padding or right padding variable

Enjoy.

How to grep inside a folder

This is how we do it

grep -nr string my_directory

Decoding http response with gzip encoding in python

Here is the function to use:

import gzip
import StringIO
import zlib

def decode (page):
    encoding = page.info().get("Content-Encoding")    
    if encoding in ('gzip', 'x-gzip', 'deflate'):
        content = page.read()
        if encoding == 'deflate':
            data = StringIO.StringIO(zlib.decompress(content))
        else:
            data = gzip.GzipFile('', 'rb', 9, StringIO.StringIO(content))
        page = data.read()

    return page

Twitter oauth2 application only using python

Here is the first method using urllib library

import urllib
import base64
import httplib&lt;/code&gt;</pre>

CONSUMER_KEY = 'my_key'
CONSUMER_SECRET = 'my_secret'
encoded_CONSUMER_KEY = urllib.quote(CONSUMER_KEY)
encoded_CONSUMER_SECRET = urllib.quote(CONSUMER_SECRET)

concat_consumer_url = encoded_CONSUMER_KEY + ":" + encoded_CONSUMER_SECRET

host = 'api.twitter.com'
url = '/oauth2/token/'
params = urllib.urlencode({'grant_type' : 'client_credentials'})
req = httplib.HTTPSConnection(host)
req.putrequest("POST", url)
req.putheader("Host", host)
req.putheader("User-Agent", "My Twitter 1.1")
req.putheader("Authorization", "Basic %s" % base64.b64encode(concat_consumer_url))
req.putheader("Content-Type" ,"application/x-www-form-urlencoded;charset=UTF-8")
req.putheader("Content-Length", "29")
req.putheader("Accept-Encoding", "utf-8")

req.endheaders()
req.send(params)
resp = req.getresponse()

print resp.status, resp.reason
print resp.read()

This is the Second Method using pycurl

import sys # used for the storage class
import pycurl # used for curling
import base64 # used for encoding string
import urllib # used for enconding
import cStringIO # used for curl buffer grabbing
import json # used for decoding json token
import time # used for stuff to do with the rate limiting
from time import sleep # used for rate limiting
from time import gmtime, strftime # used for gathering time

def get_bearer_token(consumer_key,consumer_secret):
	# enconde consumer key
	consumer_key = urllib.quote(consumer_key)
	# encode consumer secret
	consumer_secret = urllib.quote(consumer_secret)
	# create bearer token
	bearer_token = consumer_key+':'+consumer_secret
	# base64 encode the token
	base64_encoded_bearer_token = base64.b64encode(bearer_token)
	# set headers
	headers = [
	"POST /oauth2/token HTTP/1.1",
	"Host: api.twitter.com",
	"User-Agent: shobhit Twitter Application-only OAuth App Python v.1",
	"Authorization: Basic "+base64_encoded_bearer_token+"",
	"Content-Type: application/x-www-form-urlencoded;charset=UTF-8",
	"Content-Length: 29"]
	token_url = "https://api.twitter.com/oauth2/token"
	buf = cStringIO.StringIO()
	access_token = ''
	pycurl_connect = pycurl.Curl()
	pycurl_connect.setopt(pycurl_connect.URL, token_url) # used to tell which url to go to
	pycurl_connect.setopt(pycurl_connect.WRITEFUNCTION, buf.write) # used for generating output
	pycurl_connect.setopt(pycurl_connect.HTTPHEADER, headers) # sends the customer headers above
	pycurl_connect.setopt(pycurl_connect.POSTFIELDS, 'grant_type=client_credentials')
        pycurl_connect.perform() # perform the curl
	access_token = buf.getvalue() # grab the data
	pycurl_connect.close() # stop the curl
	x = json.loads(access_token)
	bearer = x['access_token']
	return bearer

Library not loaded: libmysqlclient.16.dylib error

Try making this symbolic link and it should work

sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib

#################################################################################
PS: Check the libmysqlclient path which can be done via locate libmysqlclient

Permission Error PEM File while doing ssh at Amazon EC2

If you are getting error like this

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0444 for '/Users/amazon.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: /Users/amazon.pem
Permission denied (publickey).

then you need to do is this:

chmod 400 mykey.pem

Taken from Amazon’s instructions –

Your key file must not be publicly viewable for SSH to work. Use this command if needed: chmod 400 mykey.pem

How do I permanently delete my Facebook account?

If you deactivate your account, your timeline disappears from the Facebook service immediately. People on Facebook won’t be able to search for you, though some info, like messages you sent, may still be visible to others. We also save your timeline information (ex: friends, photos, interests, etc.) in case you want to come back.

If you don’t think you’ll use Facebook again, you can request to have your account permanently deleted. Please keep in mind that you won’t be able to reactivate your account or retrieve anything you’ve added. Before you do this, you may want to download a copy of your info from Facebook. Then, if you’d like your account permanently deleted with no option for recovery, log into your account and fill out this form.

If you can’t log in to your account, you’ll need to reset your password first. To do this, go to http://www.facebook.com and click the Forgot your password? link below the password field. Once you’ve followed the instructions to reset your password and can log into your account, you can deactivate or delete your account using the steps outlined above.

SSH login without password

This is the method to connect ssh without password because sometimes it becomes irritating.

How to do it

Open your terminal and type

shobhit@mac :~> ssh-keygen -t rsa

Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory ‘/home/a/.ssh’.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 shobhit@mac

Now login to ssh using your password.

shobhit@vpc mkdir -p .ssh
shobhit@vpc vim .ssh/authorized_keys
Now type :wq to create a Blank File

Now at your Terminal. This is the last time you will be using your password

shobhit@mac:~> cat .ssh/id_rsa.pub | ssh shobhit@vpc ‘cat >> .ssh/authorized_keys’
shobhit@mac’s password:
From now on you can log into B as b from A as a without password:

shobhit@mac:~> ssh shobhit@vpc hostname

A note from one of our readers: Depending on your version of SSH you might also have to do the following changes:

Put the public key in .ssh/authorized_keys2
Change the permissions of .ssh to 700
Change the permissions of .ssh/authorized_keys2 to 640