polars.Expr.meta.is_column_selection#
- Expr.meta.is_column_selection(*, allow_aliasing: bool = False) bool [source]#
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.
Added 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