Change last_value to use function builder instead of explicitly passi…

…ng values

python/datafusion/functions.py

@@ -1701,23 +1701,13 @@ def first_value(
     )
 
 
-def last_value(
-    arg: Expr,
-    distinct: bool = False,
-    filter: bool = None,
-    order_by: Expr | None = None,
-    null_treatment: common.NullTreatment | None = None,
-) -> Expr:
-    """Returns the last value in a group of values."""
-    return Expr(
-        f.last_value(
-            arg.expr,
-            distinct=distinct,
-            filter=filter,
-            order_by=order_by,
-            null_treatment=null_treatment,
-        )
-    )
+def last_value(arg: Expr) -> Expr:
+    """Returns the last value in a group of values.
+
+    To set parameters on this expression, use ``.order_by()``, ``.distinct()``,
+    ``.filter()``, or ``.null_treatment()``.
+    """
+    return Expr(f.last_value(arg.expr))
 
 
 def bit_and(arg: Expr, distinct: bool = False) -> Expr:
@@ -1746,4 +1736,5 @@ def bool_or(arg: Expr, distinct: bool = False) -> Expr:
 
 
 def lead(arg: Expr, shift_offset: int = 1, default_value: pa.Scalar | None = None):
+    """Create a lead window function."""
     return Expr(f.lead(arg.expr, shift_offset, default_value))

src/functions.rs

@@ -349,32 +349,8 @@ pub fn first_value(
 }
 
 #[pyfunction]
-pub fn last_value(
-    expr: PyExpr,
-    distinct: bool,
-    filter: Option<PyExpr>,
-    order_by: Option<Vec<PyExpr>>,
-    null_treatment: Option<NullTreatment>,
-) -> PyResult<PyExpr> {
-    let agg_fn = functions_aggregate::expr_fn::last_value(vec![expr.expr]);
-
-    // luckily, I can guarantee initializing a builder with an `order_by` default of empty vec
-    let order_by = order_by
-        .map(|x| x.into_iter().map(|x| x.expr).collect::<Vec<_>>())
-        .unwrap_or_default();
-    let mut builder = agg_fn.order_by(order_by);
-
-    if distinct {
-        builder = builder.distinct();
-    }
-
-    if let Some(filter) = filter {
-        builder = builder.filter(filter.expr);
-    }
-
-    builder = builder.null_treatment(null_treatment.map(DFNullTreatment::from));
-
-    Ok(builder.build()?.into())
+pub fn last_value(expr: PyExpr) -> PyExpr {
+    functions_aggregate::expr_fn::last_value(vec![expr.expr]).into()
 }
 
 #[pyfunction]