Form fields - should be OrderedDict?

[אורי‎]

Django developers,

When trying to upgrade Django from 2.2 to 3.0, I encountered a problem because form fields were changed from OrderedDict to a dict. I asked on Stack Overflow and got an answer, which was to change the definition of self.fields in my form to OrderedDict ( https://stackoverflow.com/questions/61140458/how-do-i-specify-order-of-fields-in-django-form ). So I'm asking - why not change form fields to OrderedDict? Why was it changed to dict in the first place? Is there any advantage of using dict? I think changing to dict (from OrderedDict) in Django 3.0 is a mistake and it should be changed back to OrderedDict.

Thanks,

Uri.

אורי

u...@speedy.net

[James Bennett]

The purpose of OrderedDict is that it's a dictionary type where
iteration yields keys in the order they were inserted. In older
versions of Python, this was not guaranteed, so a special ordered
version was needed.

Django 3.0 supports only Python 3.6 and newer; as of Python 3.6,
iterating a normal dict yields the keys in insertion order (and this
is now a guaranteed part of the Python language specification). So
there is no longer any reason, in Django 3.0, to use OrderedDict for
situations that require insertion-ordered keys.

[אורי‎]

Hi James,

In this form I need to insert fields in the beginning of the form, and therefore I call move_to_end. It worked with Django 2.2 but not with 3.0 because this method is not defined in a dict. So I think if you revert to using OrderedDict, users will be able to use this method to insert fields in the beginning, or change the order of fields. So I think it was a mistake changing it to a dict.

אורי

u...@speedy.net

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[James Bennett]

On Fri, Apr 10, 2020 at 10:40 PM ‫אורי‬‎ <u...@speedy.net> wrote:‬
> In this form I need to insert fields in the beginning of the form, and therefore I call move_to_end. It worked with Django 2.2 but not with 3.0 because this method is not defined in a dict. So I think if you revert to using OrderedDict, users will be able to use this method to insert fields in the beginning, or change the order of fields. So I think it was a mistake changing it to a dict.

Reordering the fields of a form is a use case that already has supported API:

https://docs.djangoproject.com/en/3.0/ref/forms/api/#notes-on-field-ordering

You can either set the field_order attribute explicitly to the order
you want, or call the order_fields() method and pass in the new order.

Manually manipulating the underlying fields dict was never a
documented (and thus never a supported) feature of forms. If you need
to reorder fields, please just use the documented and supported API
for this.

[אורי‎]

Hi James,

Thanks for your feedback. I updated my code and submitted a new answer to my question on Stack Overflow.

אורי

u...@speedy.net

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