Auto Generate Forms With Django's ModelForm

Randall
Fri, 12 Mar 2010 08:06:57 +0000

In this short article, we'll analyze a better way (in some cases) to create forms for your Django models.

If you've ever worked with Django forms, then you know that there is a lot of repetitive code involved in the process of writing a form to create your model. Take, for instance, the following model, which represents a physical server (somewhere):

from django.db import models

class Server(models.Model):
    """
    This class represents a physical server.
    """
    hostname = models.CharField('Server Name',
        help_text = 'Hostname of the server.',
        max_length = 50
    )
    ip = models.IPAddressField('Server IP Address',
        help_text = 'Public IP of the server.',
        unique = True
    )
    disk_space = models.IntegerField('Disk Space on Server',
        help_text = 'Total disk space in MB.'
    )
    ram = models.IntegerField('RAM on Server',
        help_text = 'Total RAM in MB.'
    )
    cpu = models.IntegerField('Processing Power',
        help_text = 'Total Processing Power in MHz.'
    )

    def __unicode__(self):
        """
        Make the model human readable.
        """
        return self.hostname

Our Server model contains several attributes which define a Server object.

If you want to create a Server object, you can generate a form class which can be used to create a new Server model and store it in the database. This isn't very difficult, but is a bit repetitive. Here's how you would generate a form to create a new Server model using Django's forms:

from django import forms

class CreateServerForm(forms.Form):
    """
    Create a new Server model.
    """
    hostname = forms.CharField(
        label = 'Server Name',
        max_length = 50,
        required = False
    )
    ip = forms.IPAddressField )
        label = 'Public IP',
        required = False
    )
    disk_space = forms.IntegerField(
        label = 'Disk Space in MB',
        required = False
    )
    ram = forms.IntegerField(
        label = 'RAM in MB',
        required = False
    )
    cpu = forms.IntegerField(
        label = 'CPU in MHz',
        required = False
    )

As you can see, there's a lot of repetitive code in there. This is great when you need maximum control of your forms, but is overkill if you're just trying to build a simple view to create an instance of your model class.

What if there was a way to auto-generate a form class without re-writing all of that code? Well, there is! Django's ModelForm class allows you to create a very simple ModelForm without ever touching form code.

Here's our models.py code re-written using ModelForm:

from django.db import models
from django.forms import ModelForm

class Server(models.Model):
    """
    This class represents a physical server.
    """
    hostname = models.CharField('Server Name',
        help_text = 'Hostname of the server.',
        max_length = 50
    )
    ip = models.IPAddressField('Server IP Address',
        help_text = 'Public IP of the server.',
        unique = True
    )
    disk_space = models.IntegerField('Disk Space on Server',
        help_text = 'Total disk space in MB.'
    )
    ram = models.IntegerField('RAM on Server',
        help_text = 'Total RAM in MB.'
    )
    cpu = models.IntegerField('Processing Power',
        help_text = 'Total Processing Power in MHz.'
    )

    def __unicode__(self):
        """
        Make the model human readable.
        """
        return self.hostname

class ServerForm(ModelForm):
    """
    Auto generated form to create Server models.
    """
    class Meta:
        model = Server

Look how much simpler that is! Instead of writing a forms.py file, and manually creating a form, we just use ModelForm to specify a model class that Django should magically create a form from.

Lastly, let's see how we can use this new ModelForm class in an actual view. It's easy, I promise:

from myapp.models import Server
from myapp.models import ServerForm

from django.template import RequestContext
from django.shortcuts import render_to_response

def create_server(request):
    """
    Create a new Server model.
    """
    if request.method == 'POST':
        form = ServerForm(request.POST)
        if form.is_valid():

            # Create a new Server object.
            form.save()
    else:
        form = ServerForm()

    variables = RequestContext(request, {
        'form': form
    })
    return render_to_response('path/to/template/create.html', variables)

See how easy that is? In only a few lines, we were able to auto-generate a form from our model class, and then write a simple view which creates a new Server model by using the auto-generated form.

If you're interested in Django's ModelForm, read the official documentation, it will answer all of your more in-depth questions.

And of course, if you have any comments, questions, or suggestions, please post a comment.