Boston Python Workshop/Saturday/Web app project: Difference between revisions

 

This is based ''heavily'' on the official tutorial for the Django web programming framework.

 

== Writing your first Django app, part 1 ==

choice = models.CharField(max_length=200)

votes = models.IntegerField()

 

All models in Django code are represented by a class that subclasses django.db.models.Model. Each model has a number of class variables, each of which represents a database field in the model.

'polls',

)

 

Now Django knows to include the polls app.

[<Poll: Poll object>]

 

 

class Poll(models.Model):

 

Note the addition of import datetime to reference Python's standard datetime module.

 

 

>>> from polls.models import Poll, Choice

If you want to search your database, you can do it using the '''filter''' method on the ''objects'' attribute of Poll. For example:

 

[<Poll: What's up?>]

1

 

Right now, we have a Poll in the database, but it has no Choices. See:

 

>>> p.choice_set.all()

[]

<Choice: The sky>

>>> c = p.choice_set.create(choice='Just hacking again', votes=0)

<Choice: Just hacking again>

 

ROOT_URLCONF = 'workshop_mysite.urls'

 

 

 

from django.conf.urls.defaults import *

 

(r'^polls/(\d+)/vote/$', 'polls.views.vote'),

)

This is worth a review. When somebody requests a page from your Web site -- say, "/polls/23/", Django will load the ''urls.py'' Python module, because it's pointed to by the ROOT_URLCONF setting. It finds the variable named urlpatterns and traverses the regular expressions in order. When it finds a regular expression that matches -- r'^polls/(\d+)/$' -- it loads the function detail() from polls/views.py. Finally, it calls that detail() function like so:

 

return HttpResponse("Hello, world. You're at the poll index.")

 

 

 

def detail(request, poll_id):

return HttpResponse("You're voting on poll %s." % poll_id)

 

 

=== Write views that actually do something ===

All Django wants is that HttpResponse. Or an exception.

 

 

from polls.models import Poll

return HttpResponse(output)

 

 

from django.shortcuts import render_to_response

</pre>

 

 

=== Raising 404 ===

 

 

from django.http import Http404

def detail(request, poll_id):

try:

except Poll.DoesNotExist:

raise Http404

The new concept here: The view raises the Http404 exception if a poll with the requested ID doesn't exist.

 

 

<pre>

</pre>

 

 

 

 

=== Adding more detail ===

 

Method-calling happens in the {% for %} loop: poll.choice_set.all is interpreted as the Python code poll.choice_set.all(), which returns a sequence of Choice objects and is suitable for use in the {% for %} tag.

 

=== Adding some style ===

* Since we're creating a POST form (which can have the effect of modifying data), we need to worry about Cross Site Request Forgeries. Thankfully, you don't have to worry too hard, because Django comes with a very easy-to-use system for protecting against it. In short, all POST forms that are targeted at internal URLs should use the {% csrf_token %} template tag.

 

 

<pre>

</pre>

 

 

Now, let's create a Django view that handles the submitted data and does something with it. Remember, in Tutorial 3, we created a URLconf for the polls application that includes this line:

Okay, not quite finally. You might need to go to https://admin.alwaysdata.com/advanced/processes/ and click ''Restart my applications''.

 

 

 

 

== Part 4: Editing your polls in the Django admin interface ==

 

That's the basics of the Django admin interface!

 

== Part 4.5: Deploy again, again! ==