Django ModelFormSets

ModelFormsets in a Django is an advanced way of handling multiple forms created using a model and use them to create model instances. In other words, ModelFormsets are a group of forms in Django. One might want to initialize multiple forms on a single page all of which may involve multiple POST requests, for example

class McatutorialsModel(models.Model):
    title = models.CharField(max_length = 200)
    description = models.TextField()

Now if one wants to create a modelformset for this model, modelformset_factory needs to be used. A formset is a layer of abstraction to work with multiple forms on the same page. It can be best compared to a data grid.

from django.forms import formset_factory
McatutorialsFormSet = modelformset_factory(Mcatutorials)

Illustration of Rendering Django ModelFormsets manually using an Example. Consider a project named mcatutorials having an app named mcatutorials.

Refer to the following articles to check how to create a project and an app in Django.

• How to Create a Basic Project using MVT in Django?
• How to Create an App in Django ?

In your mcatutorials app make a new file called models.py where you would be making all your models. To create a Django model you need to use Django Models. Let’s demonstrate how,

In your models.py Enter the following,

# import the standard Django Model 
# from built-in library 
from django.db import models 
   
# declare a new model with a name "McatutorialModel" 
class McatutorialModel(models.Model): 
  
    # fields of the model 
    title = models.CharField(max_length = 200) 
    description = models.TextField() 
  
    # renames the instances of the model 
    # with their title name 
    def __str__(self): 
        return self.title 

Let’s explain what exactly is happening, left side denotes the name of the field and to right of it, you define various functionalities of an input field correspondingly. A field’s syntax is denoted as

Field_name = models.FieldType(attributes)

Now to create a simple formset of this form, move to views.py and create a formset_view as below.

from django.shortcuts import render 
  
# relative import of forms 
from .forms import McatutorialsForm 
  
# importing formset_factory 
from django.forms import formset_factory 
  
def formset_view(request): 
    context ={} 
  
    # creating a formset 
    McatutorialsFormSet = modelformset_factory(McatutorialsForm) 
    formset = McatutorialsFormSet() 
      
    # Add the formset to context dictionary 
    context['formset']= formset 
    return render(request, "home.html", context)

To render the formset through HTML, create a html file “home.html”. Now let’s edit templates > home.html

< form method="POST" enctype="multipart/form-data"> 
    {% csrf_token %} 
    {{ formset.as_p }} 
    < input type="submit" value="Submit"> 
< /form>

All set to check if our formset is working or not let’s visit http://localhost:8000/.

Our modelformset is working completely. Let’s learn how to modify this formset to use extra features of this formset.

Django formsets are used to handle multiple instances of a form. One can create multiple forms easily using extra attribute of Django Formsets. In mcatutorials/views.py,

from django.shortcuts import render 
  
# relative import of forms 
from .models import McatutorialsModel 
  
# importing formset_factory 
from django.forms import modelformset_factory 
  
def modelformset_view(request): 
    context ={} 
  
    # creating a formset and 5 instances of McatutorialsForm 
    McatutorialsFormSet = modelformset_factory(McatutorialsModel, fields =['title', 'description'], extra = 3) 
    formset = McatutorialsFormSet() 
  
              
    # Add the formset to context dictionary 
    context['formset']= formset 
    return render(request, "home.html", context) 

The keyword argument extra makes multiple copies of same form. If one wants to create 5 forms enter extra = 5 and similarly for others. Visit http://localhost:8000/ to check if 5 forms are created.

Creating a form is much easier than handling the data entered into those fields at the back end. Let’s try to demonstrate how one can easily use the data of a model formset in a view. When trying to handle formset, Django formsets required one extra argument {{ formset.management_data }}. To know more about Management data, Understanding the ManagementForm.

In templates/home.html,

< form method="POST" enctype="multipart/form-data"> 
      
    
    {{ formset.management_data }} 
  
    
    {% csrf_token %} 
  
    
    {{ formset.as_p }} 
      
    < input type="submit" value="Submit"> 
< /form> 

Now to check how and what type of data is being rendered edit formset_view to print the data. In mcatutorials/view.py,

from django.shortcuts import render 
  
# relative import of forms 
from .forms import McatutorialsForm 
  
# importing formset_factory 
from django.forms import formset_factory 
  
def formset_view(request): 
    context ={} 
  
    # creating a formset and 5 instances of McatutorialsForm 
    McatutorialsFormSet = formset_factory(McatutorialsForm, extra = 3) 
    formset = McatutorialsFormSet(request.POST or None) 
      
    # print formset data if it is valid 
    if formset.is_valid(): 
        for form in formset: 
            print(form.cleaned_data) 
              
    # Add the formset to context dictionary 
    context['formset']= formset 
    return render(request, "home.html", context) 

Now let’s try to enter data in the formset through http://localhost:8000/

Hit submit and data will be saved in McatutorialsModel where server is running. One can use this data in any manner conveniently now.