On Wed, Apr 15, 2020 at 7:37 AM Victor Stinner <vstinner@python.org> wrote:
Le mer. 15 avr. 2020 à 05:02, Raymond Hettinger
<raymond.hettinger@gmail.com> a écrit :
> I would like to make that functionality available to the JSON module (or just about anything else that accepts a custom dict) by adding the magic methods for mappings so that this works:
>      catalog = json.load(f, object_hook=SimpleNamespace)
>      print(catalog['clothing']['mens']['shoes']['extra_wide']['quantity'])      # currently possible with dict()
>      print(catalog.clothing.mens.shoes.extra_wide.quantity])                 # proposed with SimpleNamespace()
>      print(catalog.clothing.boys['3t'].tops.quantity                                   # would also be supported

It seems like there are many projects on PyPI which provide such
features. A few examples:

* https://pypi.org/project/attrdict/ "mapping objects that allow their
elements to be accessed both as keys and as attributes"
* https://pypi.org/project/dictlib/ "Dictionary keys as object attributes"
* https://pypi.org/project/objdict/ "An ObjDict supports all normal
dict operations, but adds support for accessing and setting entries as
* https://pypi.org/project/mydict/ "dict subclass which tries to act
like JavaScript objects, so you can use the dot notation (d.foo) to
access members of the object"
* https://pypi.org/project/dpath/ "accessing and searching
dictionaries via /slashed/paths ala xpath". Example:
dpath.util.search(x, "a/b/[cd]")
* etc.

There are many variants:

* Support nested dictionaries or not
* "Path" as a string ala XPath using "/" or "." separator -versus-
don't give a direct access into nested dictionaries
* Optional default value when a key/attribute is missing
* etc.

Is there a project on PyPI which already already been battle-tested
and gained enough popularity to consider that it's now mature enough
to enter the stdlib?

+1  that was my first reaction as well.  We don't need this battery.

If you wanted to make it a more general thing, introduce a special operator for it instead of overloading ".".  Ex: copy Perl and adopt -> as the "lookup the name in a dictionary without typing quotes around the constant value" operator.  (please don't!)

by the time we're saying "JSON should decode into a structured format" we can also say very true things like "JSON data should be validated against a schema" at which point we're ultimately going to wind up reinventing https://googleapis.dev/python/protobuf/latest/google/protobuf/json_format.html and equivalent other things.


The problem is that so far, I see no clear "winner" of a "standard"
API. So maybe leaving such feature on PyPI is better for now. It seems
like these projects are opinionated about what should be the "right"
behavior :-)

And yeah, there are even more advanced tools like https://glom.readthedocs.io/

As I wrote in the issue, I would prefer to leave SimpleNamespace
unchanged. If such feature lands into the stdlib, I would prefer it to
be a new class.

Night gathers, and now my watch begins. It shall not end until my death.
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