On Sun, 16 Jul 2023 at 04:07, Jothir Adithyan <adithyanjot...@gmail.com> wrote:
>
> Chris Angelico wrote:
> > On Tue, 11 Jul 2023 at 08:05, Jothir Adithyan adithyanjot...@gmail.com
> > wrote:
> > > Assumptions:
> > > The problem statement is based on a few assumptions:
> > >
> > > You prefer chaining `get` statements for cleaner code.
> > > You expect at least some of the `get` methods to return `None`.
> > > You want to avoid the hassle of using `try` and `except` for every `get`
> > > chain.
> > >
> > > The main assumption here is that None is a perfectly valid value in
> > your data, and should be equivalent to the key being omitted. I think
> > this is uncommon enough to be better done with custom code. But
> > fortunately, there's a really cool way to write that custom code, and
> > that's a path lookup - this is a sort of function that I've written in
> > a lot of these situations. Using your examples:
> > > import contextlib
> > > parent_dict = PlayDict()
> > > parent_dict['k1'] = None
> > > parent_dict['k2'] = {"child_key": "val"} # Parent dict can contain nested
> > > dicts
> > > with contextlib.suppress(AttributeError):
> > > result = parent_dict.get("k1", {}).get("child_key") # This will raise
> > > AttributeError
> > > result = parent_dict.get_or("k1", default={},
> > > arbitrary={}).get("child_key") # This will work
> > > I'd write it like this:
> > def lookup(basis, *keys, default=None):
> > for key in keys:
> > basis = basis.get(key)
> > if basis is None: return default
> > return basis
> > result = lookup(parent_dict, "k1", "child_key")
> > This quite tidily expresses the intent ("delve into this dictionary
> > and follow this path, returning None if there's nothing there"), and
> > is compact, with no repetition. It's a relatively short helper
> > function too, and easy to change into other forms. For example, here's
> > another version that I use, which guarantees to always return a
> > dictionary:
> > def lookup(basis, *keys):
> > for key in keys:
> > if key not in basis: basis[key] = {}
> > basis = basis[key]
> > return basis
> > Etcetera. Flexible and very handy.
> > ChrisA
> Hey Chris, thank you for your time and insight.
>
> I've thought about this for some time, and I believe that adding this feature
> could indeed be a useful and concise helper for many Python users, especially
> for API integrations and web scraping where encountering None values is quite
> common. Do you think it would be feasible to modify the existing get function
> to include a new parameter or perhaps introduce a new function altogether?
>
> I'm trying to understand why this idea may not be considered favorable. What
> are the reasons for not having this feature? What makes the current approach
> better than having this additional functionality?
>
The reason it's not a good fit for the language itself is that there
are lots of small variations. I gave you one other slight variant in
my example, and there are myriad other small differences that could
show up. So it's best for it to be part of your own toolkit. I would
strongly recommend giving the "path lookup" function style a try; it's
actually way more expressive than chained lookups, in the situations
that it's appropriate to.
ChrisA
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