Django form: what is the best way to modify posted data before validating?

Question

form = ContactForm(request.POST)

# how to change form fields' values here?

if form.is_valid():
    message = form.cleaned_data['message']

Is there a good way to trim whitespace, modify some/all fields etc before validating data?

Answer 1

You should make request.POST(instance of QueryDict) mutable by calling copy on it and then change values:

post = request.POST.copy() # to make it mutable
post['field'] = value
# or set several values from dict
post.update({'postvar': 'some_value', 'var': 'value'})
# or set list
post.setlist('list_var', ['some_value', 'other_value']))

# and update original POST in the end
request.POST = post

QueryDict docs - Request and response objects

Answer 2

You could also try using request.query_params.

1. First, set the _mutable property of the query_params to True.

2. Change all the parameters you want.

   request.query_params._mutable = True
   request.query_params['foo'] = 'foo'
   

The advantage here is you can avoid the overhead of using request.POST.copy().

Answer 3

You can do the following (as suggested by Antony Hatchkins)

If using DRF

request.data._mutable = True
request.data['key'] = value

In Django

request.POST._mutable = True
request.POST['key'] = value