On Mon, Oct 7, 2019, at 09:22, Rhodri James wrote:
> On 04/10/2019 20:34, Caleb Donovick wrote:
> > The first and perhaps the most obvious, is doing relational queries.
> > ```
> > where_x_1 = db[x=1]
> > ```
> > is more beautiful than
> > ```
> > where_x_1 = db[dict(x=1)]
> > where_x_1 = db[{'x': 1}]
> > # or by abusing slices
> > where_x_1 = db['x':1]
> > # or in the style of Pandas
> > where_x_1 = db[db['x'] == 1]
> > ```
>
> OK, I'm not sure what you're trying to do here, which all on its own
> says that what you're doing isn't self-explanatory. Would I be right in
> thinking you want a shorthand for:
>
> where_x_1 = [k for k,v in db if v == 1]
>
> If so, I'd rather the comprehension, thanks. It at least says what it does.
It'd be [v for v in db if v['x'] == 1], anyway, but the point is the list
comprehension can't be analyzed by frameworks like Pandas (to execute more
efficiently) or SqlAlchemy (to turn it into a sql query that gets executed
server-side). And for that matter can't return any type other than a list [or
generator, if you used the generator expression syntax instead]
I'm not convinced either (this is effectively a special syntax that only works
for equality, whereas you can't do db[x>=0]), but using comprehension syntax
for cases like these would require a much more sweeping change like AST
literals (something that, for example, C# has, but which can't possibly work as
smoothly as it does there without static typing)
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