You can now assign rates from a schedule of rates to a cost plan

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

@@ -0,0 +1,17 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_item": None, "cost_rate": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for cost_value in self.settings["cost_item"].CostValues:
+            ifcopenshell.api.run(
+                "cost.remove_cost_item_value", self.file, parent=self.settings["cost_item"], cost_value=cost_value
+            )
+        # This is an assumption, and not part of the official IFC documentation
+        self.settings["cost_item"].CostValues = self.settings["cost_rate"].CostValues

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

@@ -1,9 +1,19 @@
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
-        self.settings = {"cost_value": None}
+        self.settings = {"parent": None, "cost_value": None}
         for key, value in settings.items():
             self.settings[key] = value
 
     def execute(self):
-        self.file.remove(self.settings["cost_value"])
+        if len(self.file.get_inverse(self.settings["cost_value"])) == 1:
+            self.file.remove(self.settings["cost_value"])
+            # TODO deep purge
+        elif self.settings["parent"].is_a("IfcCostItem"):
+            values = list(self.settings["parent"].CostValues)
+            values.remove(self.settings["cost_value"])
+            self.settings["parent"].CostValues = values if values else None
+        elif self.settings["parent"].is_a("IfcCostValue"):
+            components = list(self.settings["parent"].Components)
+            components.remove(self.settings["cost_value"])
+            self.settings["parent"].Components = components if components else None