polars.Expr.meta.is_column_selection

Expr.meta.is_column_selection(*, allow_aliasing: bool = False) → bool

Indicate if this expression only selects columns (optionally with aliasing).

This can include bare columns, column matches by regex or dtype, selectors and exclude ops, and (optionally) column/expression aliasing.

New in version 0.20.30.

Parameters:

allow_aliasing

If False (default), any aliasing is not considered pure column selection. Set True to allow for column selection that also includes aliasing.

Examples

>>> import polars.selectors as cs
>>> e = pl.col("foo")
>>> e.meta.is_column_selection()
True
>>> e = pl.col("foo").alias("bar")
>>> e.meta.is_column_selection()
False
>>> e.meta.is_column_selection(allow_aliasing=True)
True
>>> e = pl.col("foo") * pl.col("bar")
>>> e.meta.is_column_selection()
False
>>> e = cs.starts_with("foo")
>>> e.meta.is_column_selection()
True
>>> e = cs.starts_with("foo").exclude("foo!")
>>> e.meta.is_column_selection()
True