Storing dynamic fields in Django forms

Question

Django's form library has a feature of form sets that allow you to process dynamically added forms. For example you would use form sets if your application has a list of bookmarks you could use form sets to process multiple forms that each represent a bookmark.

What about if you want to dynamically add a field to a form? An example would be a survey creation page where you can dynamically add an unlimited number of questions. How do you handle this in Django?

score 7 · Accepted Answer · answered Mar 24 '10 at 10:44

Look at this recent post by Jacob Kaplan-Moss, one of the original founders of Django: "Dynamic form generation". It uses an example to show you the process step by step. Great read.

There is also a 2008 article by James Bennett, Django's release manager.

score 5 · Answer 2 · edited Dec 22 '13 at 14:35

5

To add, remove and change fields on a Form or ModelForm, just override __init__() like this:

class MyForm(forms.Form):
def __init__(self, *args, **kwargs):
    user = kwargs.pop('user')
    other_stuff = kwargs.pop('stuff')

    super(MyForm, self).__init__(*args, **kwargs)

    self.fields['my_dynamic_field'] = forms.Field(...)

    # Add fields based on user or other_stuff

And use it like this: form = MyForm(user = user, stuff = stuff)

edited Dec 22 '13 at 14:35

garcianavalon

745
6
12

answered Mar 24 '10 at 08:28

knutin

5,033
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Note: I can´t send the user kwarg to super __init__ ; raise "__init__() got an unexpected keyword argument 'user'" – ecdani Apr 02 '13 at 11:19
Solved: kwargs.pop must come before super call – ecdani Apr 02 '13 at 11:29

score 5 · Answer 3 · answered Mar 24 '10 at 09:03

In python you can instantiate a class dynamically. knutin shows a good example of dynamically customizing a form based, and adding a few fields.

You may also create the whole form dynamically, as taken from the example given by James Bennett:

def make_contact_form(user):
    fields = { 'name': forms.CharField(max_length=50),
           'email': forms.EmailField(),
           'message': forms.CharField(widget=forms.Textarea) }
    if not user.is_authenticated():
    fields['captcha'] = CaptchaField()
    return type('ContactForm', (forms.BaseForm,), { 'base_fields': fields })

Storing dynamic fields in Django forms

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