Accessing form fields as properties in a django view

Question

According to the Django tutorial, you should access form fields using cleaned_data dictionary. I\'m wondering why I can\'t access the properties of the form directly? My for

Answer 1

The way you define fields using django.forms is just a convenient, declarative syntax; it's not really representative of what the final Form class, or an instance of it, looks like in terms of attributes.

Forms have a metaclass (without getting too deep into it, a metaclass is to declaring a class using the class keyword as an __init__ method is to creating an instance of a class using parentheses -- a hook to customise the object being created, which in the case of a metaclass, is a class!) which picks off Fields from the form class at definition time and adds them to a base_fields dict. When you instantiate a form, its base_fields are deep-copied to a fields attribute on the instance.

One point of confusion might be that you use . to access fields for display in templates -- what's actually happening there is that Django's template engine first attempts to use dictionary-style [] access to resolve property lookups and the base form class defines a __getitem__ method to take advantage of this, looking up the appropriate field from the form instance's fields dict and wrapping it with a BoundField, a wrapper which knows how to use the field and data from the form for displaying the field.