You've given some examples of what flatten() does, but I still don't
really understand how it's expected to work. Could you provide a
specification, rather than just examples? Also, I've never needed a
function like this in anything I've ever done - that may mean nothing,
but it does suggest that you need to demonstrate that it's a generally
useful tool (maybe by pointing to examples of "real world" code in
various contexts that would be improved by using it). There's a lot of
pressure to keep the stdlib for things that are widely applicable, and
the burden of demonstrating that lies with the proposer.
As the proposal stands here, I honestly don't see anything that
suggests this wouldn't be better as a standalone function published on
PyPI.
Paul
On Wed, 21 Jul 2021 at 13:43, Sven Voigt <svenpvo...@gmail.com> wrote:
>
> Hello Python-ideas,
>
> I am working with lots of JSON objects in my work and need to obtain JSON
> pointers to particular components of a JSON object. These pointers are
> defined as part of the JSON-LD specifications as relative IRIs and as part of
> the JSON-Schema specifications. However, I am not aware of these pointers
> being part of the JSON specification. The pointers are really straightforward
> and follow the same syntax as other IRIs (URLs) or file paths. For example,
> the following flatten function illustrates the mapping of nested dictionaries
> and arrays to a single flat dictionary, where each nested key is mapped to a
> unique path.
>
> d = {"a": 1, "b": {"ba": 2, "bb": [{"bba": 3, "bbb": None}]}}
> flatten(d)
> >> {'a': 1, 'b/ba': 2, 'b/bb/0/bba': 3, 'b/bb/0/bbb': None}
>
> Not only does this conversion help in generating JSON pointers, but it helps
> with logic for nested data structures. Specifically, assume there is a
> dictionary, which includes nested dictionaries, lists, and tuples, and any of
> these elements are contained within another dictionary or that other
> dictionaries elements. Then it is not sufficient to simply compare the items
> of the two dictionaries to check whether the first is a subset of the other.
> However, the flat structures can be compared directly.
>
> 1. A nested dictionary is a subset of another nested dictionary. The flatten
> function ensures the nested dictionaries are not checked for equivalence but
> subset of.
> # Current
> {"a": 1, "c": {"d": 4}}.items() <= {"a": 1, "b": 2, "c": {"d": 4, "e":
> 5}}.items()
> >> False
> # Proposed
> flatten({"a": 1, "c": {"d": 4}}).items() <= flatten({"a": 1, "b": 2, "c":
> {"d": 4, "e": 5}}).items()
> >> True
>
> 2. A nested list or tuple is a subset of a dictionary.
> # Current
> {"a": 1, "c": [3]}.items() <= {"a": 1, "b": 2, "c": [3,3]}.items()
> >> False
> # Proposed
> flatten({"a": 1, "c": [3]}).items() <= flatten({"a": 1, "b": 2, "c":
> [3,3]}).items()
> >> True
>
> Note that these examples only have one level of nesting, but the flatten
> function must handle any level of nesting. For the current version of the
> flatten function, I essentially borrowed the JSON "dumps" source code.
> However, the dumps code doesn't utilize any other functions and I believe
> there may be a missing "nestedIter" function in python. This function could
> be used for JSON dumps or flatten or anytime someone wants to visit all
> nested elements of a dictionary and perform some operation. Therefore, I
> think this function could be included in the JSON library if python-ideas
> thinks that the pointers are very specific to JSON or the itertools library,
> where the nested iteration function could be generally used for all nested
> data types.
>
> Let me know what you think of this proposal and I am looking forward to your
> responses.
>
> Best,
> Sven
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