polars.apply#

polars.apply(
exprs: Sequence[str | Expr],
function: Callable[[Sequence[Series]], Series | Any],
return_dtype: PolarsDataType | None = None,
*,
returns_scalar: bool = True,
) Expr[source]#

Apply a custom/user-defined function (UDF) in a GroupBy context.

Deprecated since version 0.19.0: This function has been renamed to map_groups().

Parameters:
exprs

Input Series to f

function

Function to apply over the input

return_dtype

dtype of the output Series

returns_scalar

If the function returns a single scalar as output.

Returns:
Expr

Expression with the data type given by return_dtype.