django - Add data to ModelForm object before saving

Question

Say I have a form that looks like this:

forms.py

class CreateASomethingForm(ModelForm):
    class Meta:
        model = Something
        fields = ['field2', 'field3', 'field4']

I want the form to have these three fields. However my Somethingclass also has field1. My question is - how do I add data to field1, if I am not using the ModelForm to collect the data. I tried doing something like this, but it isn't working and I am unsure on the proper way to solve this:

views.py

def create_something_view(request):
    if (request.method == 'POST'):
        # Create an object of the form based on POST data
        obj = CreateASomething(request.POST)
        # ** Add data into the blank field1 ** (Throwing an error)
        obj['field1'] = request.user
        # ... validate, save, then redirect 

The error I receive is:

TypeError: 'CreateAClassForm' object does not support item assignment

In Django, what is the proper way to assign data to a ModelForm object before saving?

Answer 1

form = CreateASomething(request.POST)
if form.is_valid():
    obj = form.save(commit=False)
    obj.field1 = request.user
    obj.save()