Better handling of dimensionless unit (#91)

ixmp4/core/iamc/data.py

@@ -13,15 +13,6 @@
 from .variable import VariableRepository
 
 
-def to_dimensionless(df: pd.DataFrame) -> pd.DataFrame:
-    if "dimensionless" in df.unit:
-        raise ValueError(
-            "Unit name 'dimensionless' is reserved, use an empty string '' instead."
-        )
-    df.replace(to_replace={"unit": ""}, value="dimensionless", inplace=True)
-    return df
-
-
 class RemoveDataPointFrameSchema(pa.DataFrameModel):
     type: Optional[Series[pa.String]] = pa.Field(isin=[t for t in DataPointModel.Type])
     step_year: Optional[Series[pa.Int]] = pa.Field(coerce=True, nullable=True)
@@ -69,7 +60,6 @@ def map_step_column(df: pd.Series):
 def normalize_df(df: pd.DataFrame, raw: bool, join_runs: bool) -> pd.DataFrame:
     if not df.empty:
         df = df.drop(columns=["time_series__id"])
-        df.unit = df.unit.replace({"dimensionless": ""})
         if raw is False:
             return convert_to_std_format(df, join_runs)
     return df
@@ -120,7 +110,6 @@ def add(
         type: Optional[DataPointModel.Type] = None,
     ):
         df = AddDataPointFrameSchema.validate(df)  # type:ignore
-        df = to_dimensionless(df.copy())
         df["run__id"] = self.run.id
         df = self._get_or_create_ts(df)
         substitute_type(df, type)
@@ -132,7 +121,6 @@ def remove(
         type: Optional[DataPointModel.Type] = None,
     ):
         df = RemoveDataPointFrameSchema.validate(df)  # type:ignore
-        df = to_dimensionless(df.copy())
         df["run__id"] = self.run.id
         df = self._get_or_create_ts(df)
         substitute_type(df, type)

ixmp4/core/optimization/scalar.py

@@ -107,8 +107,8 @@ def create(self, name: str, value: float, unit: str | Unit | None = None) -> Sca
             unit_name = unit
         else:
             # TODO: provide logging information about None-units being converted
-            # to dimensionless
-            dimensionless_unit = self.backend.units.create(name="dimensionless")
+            # if unit is None, assume that this is a dimensionless scalar (unit = "")
+            dimensionless_unit = self.backend.units.create(name="")
             unit_name = dimensionless_unit.name
 
         try:

ixmp4/core/unit.py

@@ -7,14 +7,6 @@
 from ixmp4.data.abstract import Unit as UnitModel
 
 
-def to_dimensionless(name):
-    if name == "dimensionless":
-        raise ValueError(
-            "Unit name 'dimensionless' is reserved, use an empty string '' instead."
-        )
-    return "dimensionless" if name == "" else name
-
-
 class Unit(BaseModelFacade):
     _model: UnitModel
     NotUnique = UnitModel.NotUnique
@@ -71,10 +63,12 @@ def create(
         self,
         name: str,
     ) -> Unit:
-        name = to_dimensionless(name)
-        if name.strip() == "":
+        if name != "" and name.strip() == "":
             raise ValueError("Using a space-only unit name is not allowed.")
-
+        if name == "dimensionless":
+            raise ValueError(
+                "Unit name 'dimensionless' is reserved, use an empty string '' instead."
+            )
         model = self.backend.units.create(name)
         return Unit(_backend=self.backend, _model=model)
 
@@ -92,7 +86,7 @@ def delete(self, x: Unit | int | str):
         self.backend.units.delete(id)
 
     def get(self, name: str) -> Unit:
-        model = self.backend.units.get(to_dimensionless(name))
+        model = self.backend.units.get(name)
         return Unit(_backend=self.backend, _model=model)
 
     def list(self, name: str | None = None) -> list[Unit]:

tests/core/test_scalar.py

@@ -60,7 +60,7 @@ def test_create_scalar(self, test_mp, request):
         assert scalar_1.id != scalar_2.id
 
         scalar_3 = run.optimization.scalars.create("Scalar 3", value=1)
-        assert scalar_3.unit.name == "dimensionless"
+        assert scalar_3.unit.name == ""
 
     def test_get_scalar(self, test_mp, request):
         test_mp = request.getfixturevalue(test_mp)

tests/core/test_unit.py

@@ -66,6 +66,9 @@ def test_unit_dimensionless(self, test_mp, request):
 
         assert unit1.id == unit2.id
 
+        assert "" in test_mp.units.tabulate().values
+        assert "" in [unit.name for unit in test_mp.units.list()]
+
     def test_unit_illegal_names(self, test_mp, request):
         test_mp = request.getfixturevalue(test_mp)
         with pytest.raises(ValueError, match="Unit name 'dimensionless' is reserved,"):