Preservation of dict ordering is guaranteed in Python 3.7+ so that
officially fixes this, correct?
https://mail.python.org/pipermail/python-dev/2017-December/151283.html
On Friday, January 5, 2018 at 1:14:03 PM UTC-5, Ole Laursen wrote:
>
> 2018-01-05 17:12 GMT+01:00 Tim Graham <timog...@gmail.com <javascript:>>:
> > Hi, Did you try writing a patch? I naively tried "class
> > MultiValueDict(OrderedDict):" as the only change and it doesn't pass the
> > tests. Perhaps more adaptations are required.
>
> Tried just now, and yeah it takes a little more adaptation.
> MultiValueDict is relying on __setitem__ not being called by the
> underlying dict implementation in a couple of places, e.g.
> MultiValueDict({ "foo": [ "bar"] }). I'm happy to write a little patch
> if the idea makes sense.
>
>
> > As for the motivation, I'm not sure if you described the problem in
> enough
> > detail. (i.e. what does "It makes highly dynamic form situations more
> > tedious to handle" mean?)
>
> If you are using Javascript to insert extra forms or rearrange input
> fields, and the order matters, then you can't use request.POST without
> some kind of bookkeeping workaround. Either by encoding and
> maintaining a sequence number client-side, or by adding extra fields
> to handle it.
>
>
> For instance, I have a bunch of rows like this where rows can be
> rearranged by dragging:
>
> Foo: 1___ Bar: hello______ [x]
>
> Foo: 3___ Baz: [ Choice 1 ] [x]
>
> [Add row]
>
> I'm using a form to validate each row - so each have a name prefix.
> Ideally, I could just go through request.POST.keys(), look for each
> new set of values and instantiate forms as needed.
>
>
> > If Python 3.6 preserves order, is this only an issue on Python 3.5? If
> so,
> > I'd guess there would be little motivation in making a change (if it's a
> > non-trivial change) given 3.5 will be end-of-life soon enough (2020).
>
> Unfortunately, it's only preserved as an implementation detail, if you
> write code that depends on the order being preserved, then you need to
> derive from OrderedDict. There was a thread on the Python list, and
> you can see here
>
> https://docs.python.org/3.6/whatsnew/3.6.html
>
> that they're careful not to say that dict preserves the order.
>
>
> Ole
>
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