> It captures a tiny fraction of Pandas style filtering while complicating
the syntax of Python
Sure maybe I we can't represent all filters super concisely but at least
inequalities, or any filter on single axis, would not be hard. E.g.
db[x=LT(1)] == db[db.x < 1]
Granted I don’t really see a way to express logical connectives between
filters in a beautiful way -- beyond doing something like db[filter=OR(x=1,
y=2)] which really isn't any better than db.filter(OR(x=1, y=2))
> db['x=1']
Ah yes cause parsing strings is a reasonable replacement for language
support. I have no idea why Pandas dropped support for this but I have to
imagine it's because it's horribly ugly, prone to bugs and difficult to
metaprogram. Semantically meaningful strings are terrible. Everytime I
write a string literal for any reason other than I a want human to read
that string I die a little inside. Which is part of the reason I want
db[x=1] instead of db[{'x':1}]. And yes everything is a string under the
hood in python but that doesn't make semantic strings less terrible. Really
under the hood (in assembly) everything is gotos but that doesn't make
their use better either. /rant
On Mon, Oct 7, 2019 at 10:07 PM David Mertz <me...@gnosis.cx> wrote:
> It's really not a worthwhile win. It captures a tiny fraction of Pandas
> style filtering while complicating the syntax of Python. Here's another
> Pandas filter:
>
> db[db.x < 1]
>
> No help there with the next syntax. Here's another:
>
> db[(db.x == 1) | (db.y == 2)]
>
> A much better idea doesn't require any changes in Python, just a clever
> class method. Pandas did this for a while, but deprecated it because...
> reasons. Still, the OP is free to create his version:
>
> db['x=1']
>
> Or
>
> db['x<1']
> db['x=1 or y=2']
>
> You can bikeshed the spelling of those predicates, but it doesn't matter,
> they are just strings that you can see however you decide is best.
>
> On Mon, Oct 7, 2019, 8:38 PM Steven D'Aprano <st...@pearwood.info> wrote:
>
>> On Tue, Oct 08, 2019 at 09:19:07AM +1100, Cameron Simpson wrote:
>> > On 07Oct2019 10:56, Joao S. O. Bueno <jsbu...@python.org.br> wrote:
>> > >So, in short, your idea is to allow "=" signs inside `[]` get notation
>> to
>> > >be translated
>> > >to dicts on the call,
>> >
>> > Subjectively that seems like a tiny tiny win. I'm quite -1 on this
>> idea;
>> > language spec bloat to neglible gain.
>>
>> As per Caleb's initial post, this is how Pandas currently does it:
>>
>> db[db['x'] == 1]
>>
>> Replacing that with db[x=1] seems like a HUGE win to me.
>>
>> Even db[{'x': 1}] is pretty clunky.
>>
>>
>>
>> --
>> Steven
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