Question

I have a form somewhere:

class FooForm(forms.Form):
    a_field = forms.CharField()
    not_a_field = 'hello world'

When instantiating this, and trying to access the field, I get a

>>> from baz.views import FooForm
>>> f = FooForm()
>>> f.not_a_field
'hello world'
>>> f.a_field
Traceback (most recent call last):
  File "<console>", line 1, in <module>
AttributeError: 'FooForm' object has no attribute 'a_field'

What is going on?

Answer 1

The way that Form is designed, the attributes are removed as attributes and added to the fields attribute. This is done so that we can use declarative syntax to define our Form, but can loop through the fields when the time comes.

>>> f = FooForm()
>>> f.fields['a_field']
<django.forms.fields.CharField object at 0x1750350>

You can find the logic for this in two places. django/forms/forms.py contains the class DeclarativeFieldsMetaclass and the method get_declared_fields. These two bits contain the logic to move everything into the fields list.