polars.Expr.keep_name¶
- Expr.keep_name() polars.internals.expr.Expr ¶
Keep the original root name of the expression.
Examples
A groupby aggregation often changes the name of a column. With keep_name we can keep the original name of the column
>>> df = pl.DataFrame( ... { ... "a": [1, 2, 3], ... "b": ["a", "b", None], ... } ... ) >>> df.groupby("a").agg(pl.col("b").list()).sort(by="a") shape: (3, 2) ┌─────┬────────────┐ │ a ┆ b_agg_list │ │ --- ┆ --- │ │ i64 ┆ list [str] │ ╞═════╪════════════╡ │ 1 ┆ ["a"] │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┤ │ 2 ┆ ["b"] │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┤ │ 3 ┆ [null] │ └─────┴────────────┘
Keep the original column name:
>>> df.groupby("a").agg(pl.col("b").list().keep_name()).sort(by="a") shape: (3, 2) ┌─────┬────────────┐ │ a ┆ b │ │ --- ┆ --- │ │ i64 ┆ list [str] │ ╞═════╪════════════╡ │ 1 ┆ ["a"] │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┤ │ 2 ┆ ["b"] │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┤ │ 3 ┆ [null] │ └─────┴────────────┘