polars.fold#

polars.fold(acc: IntoExpr, f: Callable[[pli.Series, pli.Series], pli.Series], exprs: Sequence[pli.Expr | str] | pli.Expr) pli.Expr[source]#

Accumulate over multiple columns horizontally/ row wise with a left fold.

Parameters:
acc

Accumulator Expression. This is the value that will be initialized when the fold starts. For a sum this could for instance be lit(0).

f

Function to apply over the accumulator and the value. Fn(acc, value) -> new_value

exprs

Expressions to aggregate over. May also be a wildcard expression.