polars.Expr.alias#

Expr.alias(name: str) → Self[source]#

Rename the expression.

Parameters:

name: The new name.

See also

map_alias
prefix
suffix

Examples

Rename an expression to avoid overwriting an existing column.

>>> df = pl.DataFrame(
...     {
...         "a": [1, 2, 3],
...         "b": ["x", "y", "z"],
...     }
... )
>>> df.with_columns(
...     pl.col("a") + 10,
...     pl.col("b").str.to_uppercase().alias("c"),
... )
shape: (3, 3)
┌─────┬─────┬─────┐
│ a   ┆ b   ┆ c   │
│ --- ┆ --- ┆ --- │
│ i64 ┆ str ┆ str │
╞═════╪═════╪═════╡
│ 11  ┆ x   ┆ X   │
│ 12  ┆ y   ┆ Y   │
│ 13  ┆ z   ┆ Z   │
└─────┴─────┴─────┘

Overwrite the default name of literal columns to prevent errors due to duplicate column names.

>>> df.with_columns(
...     pl.lit(True).alias("c"),
...     pl.lit(4.0).alias("d"),
... )
shape: (3, 4)
┌─────┬─────┬──────┬─────┐
│ a   ┆ b   ┆ c    ┆ d   │
│ --- ┆ --- ┆ ---  ┆ --- │
│ i64 ┆ str ┆ bool ┆ f64 │
╞═════╪═════╪══════╪═════╡
│ 1   ┆ x   ┆ true ┆ 4.0 │
│ 2   ┆ y   ┆ true ┆ 4.0 │
│ 3   ┆ z   ┆ true ┆ 4.0 │
└─────┴─────┴──────┴─────┘