Archive for the 'Python' Category

Django Facebook 3.0 – OAuth migration – Time to upgrade!

Facebook is migrating to HTTPS and OAuth to increase the safety of their users. Unfortunately these changes aren’t backwards compatible and will require some effort to follow. To support the new Facebook system you need to upgrade to Django Facebook 3.0 before October 1st.

In addition to the required migrations, this version also includes several new features. The largest change is the underlying Facebook API client. You can read about the improvements here or skip down to the upgrade instructions.

Open Facebook – New Python Facebook client

Open Facebook is a python client to the Facebook graph API. Currently it’s included in Django Facebook, but in time it will be spun of as a separate project. The client is supported, tested and up to date with the current version of Facebook’s graph API.
It handles connection issues cleanly and raises separate error classes for various Facebook error scenarios.
The syntax is very straightforward to use:

open_facebook = OpenFacebook(token)
#info about me
open_facebook.me()

#retrieving a page
open_facebook.get('fashiolista')

#retrieving your albums
open_facebook.get('me/albums')

#posting a message on your wall
open_facebook.set('me/feed', message='Check out Fashiolista', picture=image_url)

#setting a like
open_facebook.set('fashiolista/likes')

#fql example
result = open_facebook.fql('SELECT name FROM user WHERE uid = me()')

#authorization is handled separately from the API class
token = FacebookAuthorization.get_app_access_token()
test_user = FacebookAuthorization.create_test_user(token)

Album upload Example

Uploading pictures to Facebook is as simple as this:

open_facebook = get_facebook_graph(request)
photo_urls = [
    'http://d.fashiocdn.com/images/entities/0/6/t/p/d/0.365x365.jpg',
    'http://e.fashiocdn.com/images/entities/0/5/E/b/Q/0.365x365.jpg',
]
for photo in photo_urls:
    uploaded = open_facebook.set('me/photos', url=photo, 
        message='Fashiolista is awesome', name='FashiolistaTest'
    )

So there are good reasons to upgrade even if Facebook didn’t force us to :)

How to upgrade to 3.0

First Step – Install Django Facebook 3.0
Follow the installation instructions.

Javascript changes
In your Facebook initialization code enable OAuth.

FB.init({appId: facebookAppId, status: false, cookie: true, xfbml: true, oauth: true});

Perms has been renamed to scope.

FB.login(function() {}, {'scope' : 'offline_access'});

Django Facebook changes
The get_facebook_graph function is no longer persistent by default, if you want the old behavior use get_persistent_graph.
Furthermore the FacebookUserConverter class and the core Facebook API client are now separated. get_facebook_graph returns the core facebook API client. To go from the API class to the user converter class use something like

graph = get_facebook_graph(request)
facebook = FacebookUserConverter(graph)

That should be all.
If you are encountering problems feel free to let me know in the comments.

Last Step – Enable the new Facebook Migrations
Go to the Facebook Apps page and enable the OAuth migration.
Select your app -> About -> Advanced -> Migrations
Enable Force OAuth
Enable OAuth Migration

Background reading

Moving to OAuth 2.0 + HTTPS
Updated JavaScript SDK and OAuth 2.0 Roadmap
New Facebook Authentication Docs
PHP SDK v.3.1.1
PHP SDK v3.0.0

We’re hiring!

Do you also see the beauty in clean code? Are you experienced with high scalability web apps? Currently we’re looking for additional talent over at our Amsterdam office. Feel free to drop me a line at my personal email for more information: thierryschellenbach[at]gmail.com

Django &Facebook &Fashiolista &Javascript &Python &Web Development tschellenbach 13 Aug 2011 18 Comments

Django Facebook 2.0 – Integrating Facebook

It’s been a year since Facebook changed the web with the open graph API and their like button. Unfortunately Facebook didn’t have much developer love for the python/django platform. Django Facebook aims to make it easy to build facebook apps and integrate facebook with your website.

Key functionality

One of the strong points of Django Facebook is the ability to register users using Facebook. It ports all of Facebook’s user data to the Django user and profile models. This allows you to have a secure register/connect/login flow using Facebook, greatly reducing the barriers to start using your application. Below an example of me registering for Fashiolista using the Facebook register flow.

Me on Facebook

Me on Fashiolista

In this blog post I will explain how to get started implementing a Facebook connect flow. Django Facebook can however do quite a bit more, as you can see in the feature list below. Development over at the github repo is very active. I strongly appreciate help on improving the functionality so please fork and contribute.

Features

  • Register users using the Facebook open graph API
    • Full profile data birthday, gender, website, about me, username, email and picture
    • Support for mobile authentication
    • Fallback to registration form for entering additional data when required
  • Build Facebook Canvas applications
  • Mobile registration using Facebook
  • Execute Facebook FQL queries
  • Upload pictures to Facebook
  • Find your Facebook friends

Getting Started

Now let’s get started with building a Facebook login/connect/register flow. This post will guide you through it step by step.

Prerequisites

Create a Facebook app

Have django registration installed (other registration systems will require some small code changes)

pip install django_facebook :)

A.) Settings and more

Define these settings in your settings file.
FACEBOOK_API_KEY
FACEBOOK_APP_ID
FACEBOOK_APP_SECRET

add django facebook to your installed apps
‘django_facebook’,
add this line to your url config
(r’^facebook/’, include(‘django_facebook.urls’)),
add this line to your context processors
‘django_facebook.context_processors.facebook’,
add this to your AUTHENTICATION_BACKENDS
‘django_facebook.auth_backends.FacebookBackend’,

B.) Adjust your user Profile model

Secondly we need to be able to store the Facebook data on your user profile.
The easiest way to do this is to add the abstract model in django_facebook/models.py called FacebookProfileModel to your profile model.
After your profile is ready to store Facebook data you should have a working example at /facebook/connect/.
Let me know in the comments if something went wrong up to this point :)

C.) Design and integration

You can style the facebook form and button anyway you see fit. Over at Fashiolista we added a nice facepile for example. The basic markup is located in the example file connect.html.
We use the facebook javascript SDK for a smooth user integration. You can load the facebook JS like this:

<script src="{{ MEDIA_URL }}js/original/facebook.js" type="text/javascript"></script>
<script>
facebookAppId = '{{ FACEBOOK_APP_ID }}';
function facebookJSLoaded(){
FB.init({appId: facebookAppId, status: false, cookie: true, xfbml: true});
}
window.fbAsyncInit = facebookJSLoaded;
F = new facebookClass(facebookAppId);
F.load();
</script>

Subsequently implement a form which calls Facebook via javascript. Note that you can control which page to go to after connect using the next input field.

<form action="{% url facebook_connect %}?facebook_login=1" method="post">
<a href="javascript:void(0);" style="font-size: 20px;" onclick="F.connect(this.parentNode);">Register, login or connect with facebook</a>
<input type="hidden" value="{{ request.path }}" name="next" />
</form>
<div id="fb-root"></div>

That was all, you should now have a working registration flow using Facebook. Let me know in the comments if you encounter any difficulties.
If you want to go one step further and understand the facebook API, you can find the Facebook documentation here.
Django Facebook received tons of improvements from the python community. I’m certainly missing a few authors, but I would like to thank a few specifically:

Many thanks to (amongst many others)

More posts coming up

  • Building a facebook canvas app using Django Facebook
  • Find and invite friends using Django Facebook

We’re hiring!

Do you also see the beauty in clean code? Are you experienced with high scalability web apps? Currently we’re looking for additional talent over at our Amsterdam office. Feel free to drop me a line at my personal email for more information: thierryschellenbach[at]gmail.com

Css &Django &Events &Facebook &Fashiolista &Prototype &Python &Web Development tschellenbach 23 Jun 2011 70 Comments

Django open inviter – contact importer – python

Django open inviter is a python port of the PHP api client for openinviter.com‘s contact importer to work with Django. I build it for our fashion community, Fashiolista.com, where it is currently in production usage and fully functional. If you are a member of Fashiolista (which I highly doubt given the different audiences) you can test it by clicking find friends in your profile.

Usage is extremly straight forward:

from django_open_inviter.open_inviter import OpenInviter
o = OpenInviter()
contacts = o.contacts('example@example.com', 'test')

Get the code here.

Django &Fashiolista &PHP &Python &Web Development &YouTellMe tschellenbach 09 Aug 2010 15 Comments

Creating your own Digg/Facebook/Tweetmeme button

This quick walkthrough is going to bring you up to speed on how to create your own social bookmarking button. The three prime examples are the famous Digg button, Facebook’s like functionality and the tweetmeme button. For an implementation look slightly above this paragraph or check out mashable’s version on the left of their post.

Our button will be focusing on Fashiolista.com. Fashiolista is a social bookmarking site for fashion, which has seen rapid growth after launching at the next web. This tutorial explains the javascript (client side) aspects of the button. Feedback and improvements on the code would be greatly appreciated. You can find the full 450 lines of js on github.

This is what the end result looks like:

Compact Medium Large

Love it!

Love it!

Love it!

(If you are working on a shop in the fashion industry have a look at our installation instuctions.)

Step 1 – The markup

Its important to get the client side markup of the button right. Since other sites will be implementing this there is no way you can change it later on. The three major players each have their own way.

Facebook XFBML: Async script with XFBML or Iframe
Digg button: Async script with A elements
Tweetmeme: Normal script

<script type="text/javascript">
  //async script, fashiolista.com version
  (function() {
   var s = document.createElement('SCRIPT');
   var c = document.getElementsByTagName('script')[0];
   s.type = 'text/javascript';
   s.async = true;
   s.src = 'http://button.www.fashiolista.com/button/script/';
   c.parentNode.insertBefore(s, c);
  })();
</script>
<a class="fashiolista_button fashiolista_compact"
href="http://www.fashiolista.com/item_add_oe/">Love it!</a>

For Fashiolista we have chosen an async script approach with A elements. Normally loading a script element is a blocking operation for the browser. Loading the script async ensures faster page load times and a better experience if your site would ever go down. (Note that not all browsers support this option so it is still recommended to include the script tag at the bottom of the page). The function wrapped around the code ensures we don’t pollute the global scope. Furthermore the insertBefore in combination with a script tag technique is used by GA so should work in any scenario.

Step 2 – Creating the buttons, Iframe vs Script

The next step is to convert our A elements into actual buttons. We can choose to replace these A elements by our button’s html (digg, delicious approach) or load an iframe in their place (facebook, tweetmeme). The difference between these two approaches is actually pretty large. For Fashiolista you can see both an iframe and script approach. These are the most important differences I encountered.

Iframe vs Script

  • + Popup communication possible
    The script approach cannot communicate with popups it creates due to the same origin restrictions. The iframe however can be of the same domain as the popup and freely communicate. This gives a better user experience when for instance logging in.
  • + Easier to develop
    The iframe approach is easier to develop and requires less code.
  • + Parallel download in IE
    IE doesn’t download the count scripts in parallel, but it does do so for the IFRAMEs. Making this approach somewhat faster.
  • Independent CSS
    External sites don’t interfere with your button’s css if you use an iframe technique. The disadvantage is that it makes things likes hovers impossible to integrate with the other site. (For example Fashiolista’s compact button).
  • Independent
    The iframe approach makes it very hard for other sites to game the users like/love action. With a script approach a foreign site can simply call your javascript to fake someone loving the product. This freedom can be abused but also allows for mashups.
  • – Slower dom load
    Creating iframes takes a lot more time for the browser.
  • – Slower perceived load
    The script approach allows you to format the buttons before the data is loaded. Vastly increasing the perceived load speed.
  • – No shared functionality
    Buttons can’t share functionality. So when someone logs in for one button its is not possible to update the others.

The best choice differs for each project. For Fashiolista the more open script approach is currently the default.

Step 3 – Cross site scripting using JSONP

Essential to the bookmarking button is requesting the count for the given url. Cross site policies prevent us from using Ajax so we will do so by creating a script element.

_makeRequest: function (url) {
	//Simple create script element functionality
        var s = document.createElement('script');
        var b = document.body;

        s.setAttribute('type', 'text/javascript');
        s.setAttribute('async', 'true');
        s.setAttribute('src', url);

        b.appendChild(s);
}

The trouble with the script element is that you lack the nice APIs Ajax offers you. We work around this by using an url with a callback paramater, for example callback=button_loaded_3
The server side code then responds with something like this, executing the callback when the script is loaded.

button_loaded_3({"item_id": 26545, "url": "/item/26545/", "loves": 853})

This technique is often referred to as JSONP. We bind the response function to the global button_loaded_3 using the following code:

loadButtonInformation: function (buttonId) {
		//make a request to the script with the given callback
		var buttonInstance = this.buttonDict[buttonId];
		var buttonUrl = buttonInstance.lookupUrl;
		var path = '&url=' + encodeURIComponent(buttonUrl);
		var callbackFunctionName = 'button_loaded_' + buttonId;
		var scope = this;
		var callbackFunction = function(data) {
			//bind the scope and button id
			scope.buttonLoaded.call(scope, buttonId, data);
		};
		window[callbackFunctionName] = callbackFunction;
		this.makeRequest(this.countApi + path, callbackFunctionName, true);
}

Step 4 – Object oriented design

Since we are loading our code into someone else’s website we should be careful not to use similar variable names. We therefore hide as much code as possible in classes.

var fashiolistaClass = function(){ this.initialize.apply(this, arguments); };
fashiolistaClass.prototype = {
	//
	//Base class implementing the fashiolista button
	//
	initialize: function () {
		//load the buttons
		this.initializeCss();
		var fashiolistaButtons = this.findButtons();
		this.initializeButtons(fashiolistaButtons);
	}
}

Note that we are not simulating inheritance for these classes. Using them as simple namespaces is more than sufficient in this case.
The code is organized into 3 classes:

  • fashiolistaClass
  • fashiolistaUtilsClass
  • fashiolistaButtonClass

The first one acts as a manager (finding the buttons, instantiating fashiolistaButtonClasses and retrieving counts). Fashiolista button contains the logic for individual buttons and fashiolista utils contains some string parsing and dom load functionality.

Step 5 – Caching requests in the google app engine

appengineTo prevent our servers from getting flooded we are routing all traffic through google servers using the google app engine. button.www.fashiolista.com is connected to a google app engine account which forwards and caches requests to fashiolista.com. This setup enables your button to withstand great amounts of traffic without killing your servers. Furthermore it immediately also acts as a cdn for our web requests, speeding up load times for our international visitors. Setting up caching in the google app engine would require another blog post though. Let us know in the comments if you would like to know more about it.

Conclusion

The full client side code can be found here. This blog post covered the most essential parts. Code review and questions are more than welcome. Be sure to let us know in the comments. Furthermore if you are running a webshop in the fashion industry consider implementing the button.

More information

Improvements/ Request for code review

  • The domload technique is rather verbose, does anyone know a better method?
  • The popup communication or lack thereof is not ideal for users, is there a better method?
  • Script or Iframe what do you prefer?
  • Suggestions to make it faster?

Django &Fashiolista &Google app engine &Javascript &JQuery &Python &Web Development &YouTellMe tschellenbach 03 Aug 2010 11 Comments

Django Facebook – Open graph API implementation

Update:
This blog post is outdated, a new and vastly upgraded version of Django Facebook is now available. Read more about it here.

For Fashiolista.com Fashiolista we needed to integrate with the Facebook Open Graph API. The open graph API is a very exciting facebook project, which you can read about more here and here. The code at fashiolista.com allows you to register/login via facebook using the Open Graph API (similar to the old Facebook connect, but registration, instead of only logging in). Before you go try it out, fashiolista.com is aimed primarily at females so your girl friends facebook account is probably a better fit.

Im releasing the source code for Django Facebook on github. Its a very early release, but it might help other developers trying to implement a facebook register/loging flow using the new open graph api. See Github for requirements and installation instructions.

Update:
Birthday formats are currently giving some troubles for some users.
Fixed and tests added to prevent future problems. (note Fashiolista.com may still give errors, will be resolved during our next release).

Django &Fashiolista &Javascript &Python &Web Development tschellenbach 17 May 2010 105 Comments

Django query set iterator – for really large, querysets

When you try to iterate over a query set with about 0.5 million items (a few hundred megs of db storage), the memory usage can become somewhat problematic. Adding .iterator to your query set helps somewhat, but still loads the entire query result into memory. Cronjobs at YouTellMe.nl where unfortunately starting to fail. My colleague Rick came up with the following fix.

This solution chunks up the querying in bits of 1000 (by default). While this is somewhat heavier on your database (multiple queries) it seriously reduces the memory usage. Curious to hear how other django developers have worked around this problem.

import gc

def queryset_iterator(queryset, chunksize=1000):
    '''
    Iterate over a Django Queryset ordered by the primary key

    This method loads a maximum of chunksize (default: 1000) rows in it's
    memory at the same time while django normally would load all rows in it's
    memory. Using the iterator() method only causes it to not preload all the
    classes.

    Note that the implementation of the iterator does not support ordered query sets.
    '''
    pk = 0
    last_pk = queryset.order_by('-pk')[0].pk
    queryset = queryset.order_by('pk')
    while pk < last_pk:
        for row in queryset.filter(pk__gt=pk)[:chunksize]:
            pk = row.pk
            yield row
        gc.collect()

#Some Examples:
#old
MyItem.objects.all()

#better
MyItem.objects.all().iterator()

#even better
queryset_iterator(MyItem.objects.all())

Django snippet here.

Django &Python &Web Development &YouTellMe tschellenbach 03 Mar 2010 288 Comments

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