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devel / comp.lang.python / Re: dict.get_deep()

Re: dict.get_deep()

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From: ros...@gmail.com (Chris Angelico)
Newsgroups: comp.lang.python
Subject: Re: dict.get_deep()
Date: Mon, 4 Apr 2022 07:52:14 +1000
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by: Chris Angelico - Sun, 3 Apr 2022 21:52 UTC

On Mon, 4 Apr 2022 at 05:19, Marco Sulla <Marco.Sulla.Python@gmail.com> wrote:
>
> On Sun, 3 Apr 2022 at 18:57, Dieter Maurer <dieter@handshake.de> wrote:
> > You know you can easily implement this yourself -- in your own
> > `dict` subclass.
>
> Well, of course, but the question is if such a method is worth to be
> builtin, in a world imbued with JSON. I suppose your answer is no.

I think not, for a slightly different reason: There are many small
variants of it that might be needed. For instance, I have a system of
persistent data that is backed by a JSON file, and I have a path
function that does this:

def path(self, *parts):
ret = self.data # always a dict
for part in parts:
if part not in ret:
ret[part] = {}
self.save() # queue a save for the next idle time
ret = ret[part]
return ret

It's used something like this:

cfg = persist.path("channels", channame, "alerts", "host")

and if there had previously been no configs, you'll get back an empty
dict, not None, not an error, etc.

This version uses dictionaries only. A version that also supports
lists would require one more check before the "part not in ret" check
(probably something like "if this is a list, and you're asking for an
index higher than the current one, append elements till we get
there"), and a version that doesn't autosave wouldn't need the save()
call, etc, etc, etc.

IMO this is an extremely useful tool to have in your own toolbelt, but
I actually don't use *identical* versions of it very often. They're
usually subtly different from each other, due to the slight
differences in usage.

ChrisA