Support kwargs in select verb (dply and sql)

[machow]

Currently raises a NotImplementedError. One key decision here is where in resulting data kw vars should go. To be consistent with all other uses of select, I would say kwargs should go last, so the result order matches the function call order.

tbl_users >> select(x = _.id)

[ghost]

Would this allow column renaming in select to have the same API as column renaming in rename and column creation in mutate? i.e. Would this mean we can use select(column = _.old_column) instead of select(_.column == _.old_column)?

[machow]

Yeah, that's right. One big difference between python and R, though, is that keyword args have to go last. So you couldn't do this..

select(a=_.b, _.c)

But I guess not much to be done about that :/.

[ghost]

I guess we just have to wait for Syntactic Macros (PEP 638)!

[machow]

Ah interesting--I wonder how the PEP will fare! I thought briefly about trying to implement piping macros using codecs, but quickly backed out! https://rahul.gopinath.org/post/2019/12/25/python-macros/.