By Thierry Schellenbach

As you can see from the posts (one, two) I’ve always been a big Symfony fan. Symfony is really great, but my current favourite is clearly Django. I had to dive deep into python to use it, but it was well worth the effort.

Choosing Django:

Django has a few killer features which make it a better choice for many projects.

High Level Fields

As a starter there’s the usage of high level fields when describing your data model. This is best clarified by an example of a model definition in django:

class Author(models.Model): ip = models.IPAddressField() email = models.EmailField() company = models.ForeignKey(Company) picture = models.ImageField(upload_to='images/profile_pics', blank=True) homepage = models.URLField(verify_exists=True, blank=True)

Fields are specified by their purpose, such as Email, Url and Image. From this definition all subsequent logic such as form validation and file uploads are handled. The homepage field’s validation will even ping the url to see if it exists.

Read more: Creating Models (django project)

Form Handling

Starting with the knowledge that you have an email field you will often want a nice text input in your form with a regex to check if the email is valid. Django has all these standard use cases worked out for you. The following example clarifies this by using Django’s ModelForm. A model form is basically a normal Form class, with the fields pre-populated as one would expect it based on the given model.

#Form specification class AuthorForm(ModelForm): class Meta: model = models.User fields = ('ip','email','picture','homepage', 'company') #Using the form in the view (controller in Symfony terminology) form = AuthorForm(request.POST, instance=author_instance) if request.method == 'POST': if form.is_valid(): form.save() return HttpResponseRedirect(request.path) #In the template (view in Symfony terminology) : {{ uform.first_name }} {{ uform.first_name.errors }} {{ uform.first_name.label_tag }}

Django will display a file field for the image field, a text field for the url (with validation), a text input for the email field and a select box for the foreign key relation. Saving the result of the form to the database is as simple as calling save on the instance of the form. Writing custom widgets and field types is straightforward. Currently many localized fields such as a Dutch postal code Field and widgets are available. Symfony has been trying to emulate the Django newforms library. Unfortunately the syntax doesn’t seem very friendly. (Pity php doesn’t have metaclasses)

Read more: Forms (Django book)

Superb ORM

Probably the largest difference is caused by the ORM. In PHP both Propel and Doctrine are nice projects, but simply quite inadequate. The Django ORM is syntax heaven if you are coming from php. A small example:

#Find the first 5 authors which have a relation to a company #with the name YouTellMe (exact match) and site url that contains youtellme.nl Author.objects.filter(company__name = 'YouTellMe', company__site__icontains = 'youtellme.nl')[:5]

The possibilities of the standard Django ORM system are quite good. Your queries will be optimized into joins if you call select_related, many to many relations are supported and polymorphic keys are as well. The only part it fails at is query optimization in terms of column based lazy loading and support for complex relations. Fortunately you can fall back to using SQL alchemy, which is Python’s most prestigious ORM layer. SQL alchemy allows you exact query control for performance tuning and many more options you did not know you needed.

However it isn’t (yet, i hope) fully integrated into Django. It would really be great to see a tighter integration with SQL alchemy, but even the Django ORM strongly outperforms Doctrine and Propel.

Read more: DB api.

Python

You could see this both as an advantage or disadvantage. Discussing the differences between Python and PHP is probably best left for a later post. Suffice to say that I found my programming productivity to be substantially higher with Python compared to PHP. The disadvantage is a smaller number of available scripts, developers and hosts. If you are in a position in which you can choose, you really should give python a go. There must be a reason why YouTube and Google do ;)

Read more: Python in 10 Minutes

Speed

When arguing with my colleague about the choice of framework we conducted a speed test between Django and Symfony using Apache bench. At the time I was arguing in favor of Symfony. We compared a lightweight PHP framework, with Symfony and Django. Symfony was stripped down for performance and was only about 30% heavier compared to the lightweight framework. When comparing it to Django however, the results showed that Symfony was only able to handle half the load Django could. Using Python and Django seems to have a substantial effect on your server hardware requirements. (Note that these tests were only intended as an indication for internal usage. We didn’t test enough scenarios to be certain how the outcome would hold up on a live site. )

Symfony Still Rocks

When working with PHP Symfony is still an awesome framework. In many aspects it is even superior to Django. There are quite a few things Django could learn from Symfony:

Generic validation Classes and support for automatic js form validation

When using Symfony your javascript form validation is automatically generated. This is possible because of the usage of generic validation classes. In Django this would be hard to achieve since the validation system is not based on reusable classes.

A debug toolbar



One Symfony feature which I really miss in Django is the debug toolbar. Having an overview of your DB Queries, config settings, logging messages and caching information is very convenient. Especially for debugging a site with caching the caching indicators in Symfony are awesome. These caching indicators simply show which part of the page are taken from cache and which are freshly generated.

DRY templates

Symfony has a simple but very pleasant template tag called a component. A component tag calls a specified view and renders the corresponding template. The typical use case for this tag is sidebar with news items. You will want to show this sidebar on many pages, but you wouldn’t want to have to call that code inside each and every view which needs the sidebar. Doing so would clutter your view and hinder template caching. A nicer approach is to use a component template tag which calls the view responsible for retrieving the news from the database and rendering the sidebar template. This way of allowing the template to invoke code allows for DRY views and templates.

Clear Javascript and CSS management

In Django including a javascript or css file comes down to writing the respective tags in the template. In Symfony these things aren’t left to the template, but are set by the code. This allows for a few neat features. For instance the usage of an ajax utilizing template tag (helper in Symfony) will automatically ensure that prototype.js is loaded on that page. If you would set a textarea to rich, Symfony will automatically figure out you need TinyMCE to achieve the desired effect. Furthermore it allows for a general config file where you specify which assets should be loaded for a certain combination of application and view (in Django terminology). The main benefit of such an approach comes when you combine your css and javascript files and want to optimize the groupings. Here an example of the Symfony config:

// In the view.yml - comparable to settings.py indexSuccess: stylesheets: [mystyle1, mystyle2] javascripts: [myscript] [php] // In the Action - Controller in Django terminology $this->getResponse()->addStylesheet('mystyle1'); $this->getResponse()->addStylesheet('mystyle2'); $this->getResponse()->addJavascript('myscript'); // In the Template - The view in Django

Both are great, but Django more so

Having used both Django and Symfony I believe the two frameworks can learn a great deal from each other. Fortunately many people seem to experiment with a wide variety of frameworks (Including at least one delicious developer, version 3 of delicious maybe? ;)). Django in general has some excellent features, which make it a better choice for web development. If you are somehow bound to PHP, Symfony is still a good choice. The Django community is buzzing and active like no other and I look forward to posting on the various features.

If you didn’t try it yet:

django-project.com

djangobook.com

Note: Looking to hire Python and Javascript Coders

YouTellMe.nl is currently looking to hire Python and Javascript programmers in The Netherlands. Drop me an email at thierry [at] youtellme.com if you would like to know more or want to suggest someone for the job openings.