You can now edit the unit basis of a cost value for a schedule of rates

src/ifcopenshell-python/ifcopenshell/api/cost/edit_cost_value.py

@@ -1,3 +1,8 @@
+import ifcopenshell
+import ifcopenshell.util.unit
+import ifcopenshell.util.element
+
+
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
@@ -10,4 +15,19 @@ class Usecase:
             if name == "AppliedValue" and value is not None:
                 # TODO: support all applied value select types
                 value = self.file.createIfcMonetaryMeasure(value)
+            elif name == "UnitBasis":
+                self.remove_existing_unit_basis()
+                if value:
+                    value_component = self.file.create_entity(
+                        ifcopenshell.util.unit.get_unit_measure_type(value["UnitComponent"].UnitType),
+                        value["ValueComponent"],
+                    )
+                    value = self.file.create_entity("IfcMeasureWithUnit", value_component, value["UnitComponent"])
             setattr(self.settings["cost_value"], name, value)
+
+    def remove_existing_unit_basis(self):
+        if (
+            self.settings["cost_value"].UnitBasis
+            and len(self.file.get_inverse(self.settings["cost_value"].UnitBasis)) == 1
+        ):
+            ifcopenshell.util.element.remove_deep(self.file, self.settings["cost_value"].UnitBasis)