Python

by webjunkie on Facebook, Oauth, Postgres, Pylons, Python, SQLAlchemy

Pylons and Facebook based Authorization with OAuth 2.0

Authorizing a user using Facebook OAuth 2.0 based login it’s pretty straighfoard. This is for the person who asked a question on stackoverflow.com I hope it helps.

Add the apikey, appid and secret of my Facebook app to the development.ini file

facebook.apikey = 42bc5a4051b274ede5cb73a6cd6fad56
facebook.secret = a355e66e8c0293390896a170f9d5r4c3
facebook.appid = 20894420580890

Configure my model/init.py file:

from PRJNAME.model.meta import Session, Base
from sqlalchemy import Column
from sqlalchemy import Integer
from sqlalchemy import Unicode
from sqlalchemy import Table
from sqlalchemy import Text
from sqlalchemy import Unicode
from sqlalchemy import BigInteger
from sqlalchemy import TIMESTAMP
from sqlalchemy import ForeignKey,ForeignKeyConstraint
from sqlalchemy.orm import mapper
import datetime
def init_model(engine):
    """Call me before using any of the tables or classes in the model"""
    Session.configure(bind=engine,autoflush=True,autocommit=False)
def now():
    return datetime.datetime.now()
social_user = Table('social_user', Base.metadata,
    Column('id', Integer, primary_key=True),
    Column('oauth_provider', Text(), nullable=False),
    Column('oauth_id', Text() , nullable=False),
    Column('username', Unicode(50), nullable=False),
    Column('access_token', Unicode(200)),
    Column('created', TIMESTAMP(timezone=True), default=now()),
    )
  class Social(object):
    pass
  mapper(Social,social_user)

Download the Facebook Python-SDK

https://github.com/facebook/python-sdk

And save it on your project lib directory

Create a controller named account

~$ paster controller account

Add a view named login and render a login button

I’ll use https://graph.facebook.com/oauth/authorize as the url to start the authorization process

 import PRJNAME.lib.facebook as facebook
 import simplejson
 from pylons import config
 class AccountController(BaseController):
   def login(self):
     params = {
       'client_id':config['facebook.appid'],
       'scope' : 'offline_access,publish_stream,email', #permissions needed by the app
       'redirect_uri' : 'http://'+request.environ['HTTP_HOST']+'/account/auth'
     }
     keys = params.keys()[:]
     keys.sort()
     q_str = unicode()
     for name in keys:
       q_str+= ("&%s=%s" % (name,params[name]))
     c.login_url = 'https://graph.facebook.com/oauth/authorize?' + q_str
     return render('/website/login.html')

login.html

Login with Facebook


login with Facebook

Add a function on helpers.py

This function will create our access_token from our code request params

  import urllib
  import json
  def getAccessTokenFromCode(applicationId, applicationSecret, code,redirect_uri):
    q_str = unicode()
    params = {
      'client_id':applicationId,
      'client_secret':applicationSecret,
      'code':code,
      'redirect_uri':'http://'+request.environ['HTTP_HOST']+redirect_uri
    }
    keys = params.keys()[:]
    keys.sort()
    for name in keys:
      q_str+= ("&%s=%s" % (name, params[name]))
    url = 'https://graph.facebook.com/oauth/access_token?'+ q_str
    response = urllib.urlopen(url).read()
    result = response.split('=')[-1]
    if result:
      return result

Create an auth view on account controller

I do this because in the link button there is an argument called redirect_uri that points to http://ww.example.com/account/auth.

from PRJNAME.lib.helpers import getAccessTokenFromCode
from pylons import config
def auth(self):
if request.params.has_key('code'):
      access_token = getAccessTokenFromCode(
       config['facebook.appid'],
       config['facebook.secret'],
       request.params.get('code'),
       redirect_uri='/account/auth'
      )
      graph = facebook.GraphAPI(access_token)
      #grab the user data
      fbdata = graph.get_object("me")
      #query the db to check if user is already authorized
      q = Session.query(model.Social)
      user = q.filter_by(oauth_id=fbdata['id']).first()
      if user:
       # you can redirect to a dashboard
       return 'already in db and authorized'
      else:
      #insert user data to db
      fb = model.Social()
      fb.oauth_provider = 'Facebook'
      fb.oauth_id = fbdata['id']
      fb.username = fbdata['name']
      fb.access_token = access_token
      Session.add(fb)
      Session.commit()
      # redirect to dashboard page

And that’s pretty much it.

 
by webjunkie on DB, Pylons, Python, SQLAlchemy, uWSGI

repoze.what with reflected tables using SQLAlchemy in Pylons

One of the many things I like about SQLAlchemy is the feature of reflected tables, this means I can develop dashboards for existing applications with my current favorite framework(Pylons). So I had to create an authorization mechanism for my dashboard and this recipe from the Pylons cookbook was just what I needed.
The only thing I had to change was the way my tables were being mapped since the users table schema was already defined. This is what I did:

user_table = schema.Table('users', Base.metadata, autoload=True, autoload_with=engine)
user_group_table = schema.Table('user_groups',Base.metadata,autoload=True,autoload_with=engine)
group_permission_table = schema.Table('group_permission',Base.metadata,autoload=True,autoload_with=engine)
permission_table = schema.Table('permissions', Base.metadata,autoload=True,autoload_with=engine)
group_table = schema.Table('groups', Base.metadata,autoload=True,autoload_with=engine)
orm.mapper(User,user_table, properties={
      'groups':orm.relation(Group, secondary=user_group_table),
    })
orm.mapper(Permission,permission_table,properties={
      'groups':orm.relation(Group, secondary=group_permission_table),
    })
orm.mapper(Group,group_table,properties={
      'permissions':orm.relation(Permission, secondary=group_permission_table),
      'users':orm.relation(User, secondary=user_group_table),
    })
orm.mapper(UGT,user_group_table)
orm.mapper(GPT,group_permission_table)

And here’s the schema I had to create, except for the users table:

CREATE TABLE user_groups( 
id serial NOT NULL,  
user_id integer,  
group_id integer,  
CONSTRAINT user_groups_pkey PRIMARY KEY (id), 
CONSTRAINT gid_fkey FOREIGN KEY (group_id) REFERENCES groups (id)
CONSTRAINT uid_fkey FOREIGN KEY (user_id)   REFERENCES users (id)
)

CREATE TABLE group_permission(
id serial NOT NULL,
gid integer,
permid integer,
CONSTRAINT group_permission_pkey PRIMARY KEY (id),
CONSTRAINT groupid_fkey FOREIGN KEY (gid) REFERENCES groups (id),
CONSTRAINT permid_fkey FOREIGN KEY (permid) REFERENCES permissions (id)
)

CREATE TABLE permissions(
  id serial NOT NULL,
  pname character varying(50),
  CONSTRAINT permissions_pkey PRIMARY KEY (id)
)

CREATE TABLE groups(
  id serial NOT NULL,
  gname character varying(50),
  CONSTRAINT groups_pkey PRIMARY KEY (id)
)

CREATE TABLE users(
id serial NOT NULL,
username character varying(50),
email character varying(50),
upassword character varying(150),
CONSTRAINT users_pkey PRIMARY KEY (id)
)

And that’s all there’s to it. I was very surprise on how flexible SQLAlchemy is.

 
by webjunkie on Nginx, Pylons, Python, uWSGI

Nginx, uWSGI, Pylons and the double slash problem

So there I am, deploying my first Pylons based app and thinking on which WSGI interface to go with. At the end I decided to go with uWSGI it has been proven to be a beast at handling requests even on high loads.
I setup my Nginx conf file, fired up uWSGI and found out that all of my links had a double slash i.e //home/new. I couldn’t belive it all my hard work for nothing. After a couple of searches I found out a reply on the Nginx mailing list from Igor Sysoev saying the solution is to add the qualified param to all the url() calls.

url(controller='account', action='new', qualified=True)

Indeed that solved the problem, for a second I thought my chance for testing the performance of uWSGI was gone.
 

 
by webjunkie on Facebook, Pylons, Python

Posting to a page wall with the Facebook SDK in Python

I’ve been developing in Python for quite a few months now and the need to develop a Facebook app has arrived.
So in my app I had the need to post content to a Fan Page wall and after a couple of tests I noticed the content being posted on the Fan Page on behalf of the Page owner and not the page itself.
To fix that I had to make the following changes inside the if condition where it checks for the arguments being posted:

if post_args is not None:
  if post_args['page_token']:
    post_args["access_token"] = post_args['page_token']#self.access_token
  else:
    post_args["access_token"] = self.access_token
else:
  args["access_token"] = self.access_token

So now I’m checking for an extra argument in this case page_token, if it’s set we use that token instead of the token that was used to initialize the Facebook Graph object.
With this changes in place we add the extra parameter page_token to our attachment and it shoud work as expected, with the content being posted on behalf of the page.

graph = facebook.GraphAPI(str(access_token))
attach = {
  "name": 'Hello world',
  "link": 'http://www.example.com',
  "caption": 'test post',
  "description": 'some test',
  "picture" : 'http://www.example.com/picture.jpg'
  "page_token" : str(page_token)
}
msg = 'New content posted'
post = graph.put_wall_post(message=msg, attachment=attach,profile_id=str(page_id))
  if post:
    return 'posted'