DEPR: deprecate Term & Expr in the pd.* namespace

[jreback]

This is imported via pandas.io.api. I think making a sub-class might work that has the deprecation.

This is used internally, just want to remove the external visibility (as not been necessary for quite a few releases).

[jorisvandenbossche]

It's still used in the docs: http://pandas-docs.github.io/pandas-docs-travis/io.html#query-via-data-columns and http://pandas-docs.github.io/pandas-docs-travis/io.html#experimental

[jorisvandenbossche]

Maybe unrelated, but there is also the pd.Expr in the top-level namespace, and I don't think that is used in the docs. Would that also be a candidate for deprecation as a public top-level function?

[jreback]

yes both of these should be removed from the pd namespace

[jreback]

I think they need to have a proxy-object to provide the deprecation and then return the current object.

[jorisvandenbossche]

or would a subclass work? (in pandas/init.py or in io.api.py):

class Expr(pandas.computation.expr.Expr)

    def __init__(self, *args, **kwargs):
        warnings.warn(...)
        super(Expr, self).__init__()

[jreback]

yes a public subclass would work (and leave the current names)

[jreback]

closing in favor of #13790