How to create a formset from form-instance in Python Django

Question

I am trying to get a Django - Formset out of an instance of a form class.

In my form class i add some fields in the init method because the form has to offer some flexibility. Therefore i can't pass the class as parameter to the formset_factory function.

--forms.py

class ConfigForm(forms.Form):
    def __init__(self, fields, fields_choices, *args, **kwargs):
        super(ConfigForm, self).__init__(*args, **kwargs)

        for field in fields:
            # instanciate Field from field data
            exec(
                f'self.fields["{field.name}"] ='
                f'forms.{field.field_type.field_type}('
                f'required = {field.required},'
                f'disabled = {field.disabled},'
                f'label = "{field.label}",'
                f'initial = "{field.value}",'
                f'widget = {field.widget},'
                f'help_text = "{field.description}"'
                f')'
                )
            # if field is a ChoiceField add choices to the field instance
            if 'ChoiceField' in field.field_type.field_type:
                self.fields[field.name].choices = [fields_choices[field.name]]

--views.py ...

form = forms.ConfigForm(active_fields, field_choices)
formset = formset_factory(form, extra=1)

...

But if i try to call formset_factory with an instance of ConfigForm, the following error occurs:

Internal Server Error: /machines/testconfig/mw0-sap-001/
Traceback (most recent call last):
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\views\generic\base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\views\generic\base.py", line 97, in dispatch
    return handler(request, *args, **kwargs)
  File "D:\Users\BKU\maximilianwiederer\OneDrive - Deutsche Bahn\Documents\Programmierung\Eclipse\sap4cloud-dev\machines\views.py", line 83, in get
    formset = forms.formset_factory(form, extra=1)
  File "C:\Users\maximilianwiederer\AppData\Local\Programs\Python\Python37\lib\site-packages\django\forms\formsets.py", line 441, in formset_factory
    return type(form.__name__ + 'FormSet', (formset,), attrs)
AttributeError: 'ConfigForm' object has no attribute '__name__'

Maximilian Wiederer · Accepted Answer · 2019-11-06 15:48:48Z

1

You can't pass an instance of a form into a formset factory. It expects a class, not an instance. However, you can provide a dictionary of arguments to the factory to give to each instance of the form that is created.

https://docs.djangoproject.com/en/2.2/topics/forms/formsets/#passing-custom-parameters-to-formset-forms

Here's how I would suggest writing your code.

ConfigFormset = forms.formset_factory(forms.ConfigForm)
formset = ConfigFormset(
    form_kwargs={
        'fields' : active_fields,
        'fields_choices': {}
        }
    )

edited Nov 6, 2019 at 15:48

Maximilian Wiederer

454 bronze badges

answered Nov 6, 2019 at 14:30

Jacinator

1,4139 silver badges12 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Maximilian Wiederer Over a year ago

Thank's, you saved my day. I edited your code because you forgot one step (instanciating the ConfigFormSet and after that get the formset with the form_kwargs out of it) But now everything works fine :D

Collectives™ on Stack Overflow

How to create a formset from form-instance in Python Django

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related