selectors

xorq.api.selectors

Convenient column selectors.

Check out the blog post on selectors for examples!

Rationale

Column selectors are convenience functions for selecting columns that share some property.

Discussion

For example, a common task is to be able to select all numeric columns for a subsequent computation.

Without selectors this becomes quite verbose and tedious to write:

import ibis t = ibis.table(dict(a=“int”, b=“string”, c=“array”, abcd=“float”)) expr = t.select([t[c] for c in t.columns if t[c].type().is_numeric()]) expr.columns [‘a’, ‘abcd’]

Compare that to the numeric selector:

import ibis.selectors as s expr = t.select(s.numeric()) expr.columns [‘a’, ‘abcd’]

When there are multiple properties to check it gets worse:

expr = t.select( … [ … t[c] … for c in t.columns … if t[c].type().is_numeric() or t[c].type().is_string() … if (“a” in c or “b” in c or “cd” in c) … ] … ) expr.columns [‘a’, ‘b’, ‘abcd’]

Using a composition of selectors this is much less tiresome:

expr = t.select((s.numeric() | s.of_type(“string”)) & s.contains((“a”, “b”, “cd”))) expr.columns [‘a’, ‘b’, ‘abcd’]