minor changes

Author: RobbieKiwi

linopy/expressions.py

@@ -726,8 +726,8 @@ def const(self, value: DataArray) -> None:
         self._data = assign_multiindex_safe(self.data, const=value)
 
     @property
-    def has_constant(self) -> DataArray:
-        return self.const.any()
+    def has_constant(self) -> bool:
+        return bool(self.const.any())
 
     # create a dummy for a mask, which can be implemented later
     @property

linopy/model.py

@@ -14,7 +14,6 @@
 from pathlib import Path
 from tempfile import NamedTemporaryFile, gettempdir
 from typing import Any, Literal, ParamSpec, TypeVar, overload
-from warnings import warn
 
 import numpy as np
 import pandas as pd
@@ -83,9 +82,6 @@
 R = TypeVar("R")
 
 
-class ConstantInObjectiveWarning(UserWarning): ...
-
-
 class ConstantObjectiveError(Exception): ...
 
 
@@ -812,6 +808,7 @@ def add_objective(
         | Sequence[tuple[ConstantLike, VariableLike]],
         overwrite: bool = False,
         sense: str = "min",
+        allow_constant: bool | None = None,
     ) -> None:
         """
         Add an objective function to the model.
@@ -822,6 +819,8 @@ def add_objective(
             Expression describing the objective function.
         overwrite : False, optional
             Whether to overwrite the existing objective. The default is False.
+        allow_constant : bool, optional
+            Set the `Model.allow_constant_objective` attribute. If True, the objective is allowed to contain a constant term.
 
         Returns
         -------
@@ -838,10 +837,12 @@ def add_objective(
 
         self.objective.expression = expr
         self.objective.sense = sense
+        if allow_constant is not None:
+            self.allow_constant_objective = allow_constant
+
         if not self.allow_constant_objective and self.objective.has_constant:
-            warn(
+            raise ConstantObjectiveError(
                 "Objective function contains constant terms but this is not allowed as Model.allow_constant_objective=False, running solve will result in an error. Please either remove constants from the expression with expr.drop_constants() or set Model.allow_constant_objective=True.",
-                ConstantInObjectiveWarning,
             )
 
     def remove_variables(self, name: str) -> None:

linopy/objective.py

@@ -196,7 +196,7 @@ def has_constant(self) -> bool:
         """
         Returns whether the objective has a constant term.
         """
-        return bool(self.expression.has_constant)
+        return self.expression.has_constant
 
     @property
     def model(self) -> Model:

test/test_linear_expression.py

@@ -1242,7 +1242,7 @@ def test_drop_constant(x: Variable) -> None:
         assert all(expr_2.const.values == 0.0), (
             f"Expected constant 0.0, got {expr_2.const.values}"
         )
-        assert not bool(expr_2.has_constant)
+        assert not expr_2.has_constant
 
 
 def test_simplify_basic(x: Variable) -> None:

test/test_optimization.py

@@ -20,7 +20,7 @@
 from linopy import GREATER_EQUAL, LESS_EQUAL, Model, solvers
 from linopy.common import to_path
 from linopy.expressions import LinearExpression
-from linopy.model import ConstantInObjectiveWarning, ConstantObjectiveError
+from linopy.model import ConstantObjectiveError
 from linopy.solver_capabilities import (
     SolverFeature,
     get_available_solvers_with_feature,
@@ -958,9 +958,7 @@ def test_model_resolve(
 
 def test_model_with_constant_in_objective_feasible(model: Model) -> None:
     objective = model.objective.expression + 1
-
-    with pytest.warns(ConstantInObjectiveWarning):
-        model.add_objective(expr=objective, overwrite=True)
+    model.add_objective(expr=objective, overwrite=True)
 
     with pytest.raises(ConstantObjectiveError):
         status, _ = model.solve(solver_name="highs")
@@ -980,8 +978,7 @@ def test_model_with_constant_in_objective_infeasible(model: Model) -> None:
     model.add_constraints([(1, "x")], "<=", 0)
     model.add_constraints([(1, "y")], "<=", 0)
 
-    model.allow_constant_objective = True
-    _, condition = model.solve(solver_name="highs")
+    _, condition = model.solve(solver_name="highs", allow_constant=True)
 
     assert condition == "infeasible"
     # Even though the problem was not solved, the constant term should still be accessible
@@ -990,8 +987,7 @@ def test_model_with_constant_in_objective_infeasible(model: Model) -> None:
 
 def test_model_with_constant_in_objective_error(model: Model) -> None:
     objective = model.objective.expression + 1
-    model.allow_constant_objective = True
-    model.add_objective(expr=objective, overwrite=True)
+    model.add_objective(expr=objective, overwrite=True, allow_constant=True)
     model.add_constraints([(1, "x")], "<=", 0)
     model.add_constraints([(1, "y")], "<=", 0)
 

test/test_quadratic_expression.py

@@ -323,7 +323,7 @@ def test_drop_constant(x: Variable) -> None:
         assert all(expr_2.const.values == 0.0), (
             f"Expected constant 0.0, got {expr_2.const.values}"
         )
-        assert not bool(expr_2.has_constant)
+        assert not expr_2.has_constant
 
 
 def test_quadratic_expression_to_matrix(model: Model, x: Variable, y: Variable) -> None: