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

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

@@ -120,7 +120,11 @@ class Data:
     def load_cost_item_value(cls, cost_item_data, cost_item, cost_value):
         value_data = cost_value.get_info()
         del value_data["AppliedValue"]
-        del value_data["UnitBasis"]
+        if value_data["UnitBasis"]:
+            data = cost_value.UnitBasis.get_info()
+            data["ValueComponent"] = data["ValueComponent"].wrappedValue
+            data["UnitComponent"] = data["UnitComponent"].id()
+            value_data["UnitBasis"] = data
         if value_data["ApplicableDate"]:
             value_data["ApplicableDate"] = ifcopenshell.util.date.ifc2datetime(value_data["ApplicableDate"])
         if value_data["FixedUntilDate"]:

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)

src/ifcopenshell-python/ifcopenshell/util/unit.py

@@ -197,6 +197,10 @@ def get_property_unit(prop, ifc_file):
         return units[0]
 
 
+def get_unit_measure_type(unit_type):
+    return "Ifc" + unit_type[0:-4].lower().capitalize() + "Measure"
+
+
 def get_symbol_quantity_class(symbol):
     # Dumb, but everybody gets it, unlike regex golf
     if not symbol: