Update default importance values to 1.0 in Importance class and tests

doc/source/changelog.rst

@@ -8,13 +8,17 @@ MontePy Changelog
 #Next Release#
 --------------
 
+**Features**
+
+* Changed default importance value from 0.0 to 1.0 to match MCNP defaults. (:issue:`735`)
+
 **Documentation**
 
 * Improved documentation for NumberedObjectCollections on Slicing behavior. (:issue:`798`)
 
 **Bugs Fixed**
 
-* Fixed bug where lines that were the allowed length was raising a ``LineOverRunWarning`` when read by MontePy (:issue:`517`). 
+* Fixed bug where lines that were the allowed length was raising a ``LineOverRunWarning`` when read by MontePy (:issue:`517`).
 
 * Added descriptive TypeError messages (:issue:`801`)
 

doc/source/starting.rst

@@ -609,10 +609,10 @@ For example:
 
     >>> for particle in sorted(problem.mode):
     ...     print(particle, cell.importance[particle])
-    neutron 0.0
-    photon 0.0
+    neutron 1.0
+    photon 1.0
     >>> print(cell.importance[montepy.Particle.NEUTRON])
-    0.0
+    1.0
 
 There's also a lot of convenient ways to do bulk modifications.
 There is the :func:`~montepy.data_inputs.importance.Importance.all` property that lets you set the importance for all particles in the problem at once.
@@ -629,7 +629,10 @@ For example:
     neutron 2.0
     photon 2.0
 
-This will set the importances for the neutron and photon. 
+This will set the importances for the neutron and photon.
+
+You can also delete an importance to reset it to the default value (1.0).
+For example: ``del cell.importance.neutron``.
 
 There is also the method: :func:`~montepy.cells.Cells.set_equal_importance`.
 This method sets all of the cells for all particles in the problem to the same importance.

montepy/cell.py

@@ -227,10 +227,17 @@ def importance(self):
         Each particle's importance is a property of Importance.
         e.g., ``cell.importance.photon = 1.0``.
 
+        Deleting an importance resets it to the default value (1.0).
+        e.g., ``del cell.importance.neutron``.
+
         Returns
         -------
         Importance
             the importance for the Cell.
+
+        .. versionchanged:: 1.2.0
+
+            Default importance value changed from 0.0 to 1.0 to match MCNP defaults.
         """
         return self._importance
 

montepy/data_inputs/importance.py

@@ -52,6 +52,7 @@ def __init__(
         self._particle_importances = {}
         self._real_tree = {}
         self._part_combos = []
+        self._explicitly_set = False
         super().__init__(input, in_cell_block, key, value)
         if self.in_cell_block:
             if key:
@@ -62,6 +63,7 @@ def __init__(
                     raise ValueError(
                         f"Cell importance must be a number ≥ 0. {val.value} was given"
                     )
+                self._explicitly_set = True
                 self._part_combos.append(self.particle_classifiers)
                 for particle in self.particle_classifiers:
                     self._particle_importances[particle] = value
@@ -76,6 +78,7 @@ def __init__(
                     raise MalformedInputError(
                         input, f"Importances must be ≥ 0 value: {node} given"
                     )
+            self._explicitly_set = True
             self._part_combos.append(self.particle_classifiers)
             for particle in self.particle_classifiers:
                 self._particle_importances[particle] = copy.deepcopy(self._tree)
@@ -95,7 +98,7 @@ def _generate_default_cell_tree(self, particle=None):
             particles.particles = self._problem.mode.particles
         classifier.particles = particles
         list_node = syntax_node.ListNode("imp data")
-        list_node.append(self._generate_default_node(float, 0.0))
+        list_node.append(self._generate_default_node(float, 1.0))
         tree = syntax_node.SyntaxNode(
             "Importance",
             {
@@ -126,7 +129,7 @@ def _has_classifier():
     @property
     def has_information(self):
         if self.in_cell_block:
-            return True
+            return self._explicitly_set
 
     def merge(self, other):
         if not isinstance(other, type(self)):
@@ -163,7 +166,7 @@ def __getitem__(self, particle):
             val = self._particle_importances[particle]["data"][0]
             return val.value
         except KeyError:
-            return 0.0
+            return 1.0
 
     def __setitem__(self, particle, value):
         if not isinstance(particle, Particle):
@@ -175,6 +178,7 @@ def __setitem__(self, particle, value):
             raise ValueError("importance must be ≥ 0")
         if particle not in self._particle_importances:
             self._generate_default_cell_tree(particle)
+        self._explicitly_set = True
         self._particle_importances[particle]["data"][0].value = value
 
     def __delitem__(self, particle):
@@ -213,6 +217,7 @@ def push_to_cells(self):
                     value = self._particle_importances[particle]["data"][i]
                     # force generating the default tree
                     cell.importance[particle] = value.value
+                    cell.importance._explicitly_set = True
                     # replace default ValueNode with actual valueNode
                     tree = cell.importance._particle_importances[particle]
                     tree.nodes["classifier"] = copy.deepcopy(
@@ -284,6 +289,7 @@ def all(self, value):
         if value < 0.0:
             raise ValueError("Importance must be ≥ 0.0")
         if self._problem:
+            self._explicitly_set = True
             for particle in self._problem.mode:
                 self._particle_importances[particle]["data"][0].value = value
 
@@ -506,7 +512,7 @@ def __create_particle_imp_doc(particle_type):
 Returns
 -------
 float
-    the importance for the particle type. If not set, defaults to 0.
+    the importance for the particle type. If not set, defaults to 1.0.
 """
 
 

pyproject.toml

@@ -15,7 +15,8 @@ authors = [
 	{name = "Brenna Carbno", email="[email protected]"},
 	{name = "Benjaminas Marcinkevicius", email="[email protected]"},
 	{name = "Paul Ferney", email="[email protected]"},
-	{name = "Digvijay Yeware", email="[email protected]"}
+	{name = "Digvijay Yeware", email="[email protected]"},
+	{name = "Harsh Dayal", email="[email protected]"},
 ]
 keywords = ["MCNP", "neutronics", "imcnp", "input file", "monte carlo", "radiation transport"]
 license = "MIT"

tests/test_importance.py

@@ -28,7 +28,7 @@ def create_cell_from_input(self, in_str, block=block_type.BlockType.CELL):
                     "neutron": 1.0,
                     "photon": 1.0,
                     "all": None,
-                    "alpha_particle": 0.0,
+                    "alpha_particle": 1.0,
                     "in_cell_block": True,
                 },
                 None,
@@ -40,7 +40,7 @@ def create_cell_from_input(self, in_str, block=block_type.BlockType.CELL):
             ),
             (
                 "1 0 -1",
-                {"neutron": 0.0},
+                {"neutron": 1.0},
                 None,
             ),  # default neutron importance when nothing is set
             # Error cases
@@ -267,9 +267,9 @@ def test_importance_deleter(self, cell_with_importance):
         """
         cell = cell_with_importance
         del cell.importance.neutron
-        assert cell.importance.neutron == pytest.approx(0.0)
+        assert cell.importance.neutron == pytest.approx(1.0)
         del cell.importance[Particle.PHOTON]
-        assert cell.importance.photon == pytest.approx(0.0)
+        assert cell.importance.photon == pytest.approx(1.0)
         with pytest.raises(TypeError):
             del cell.importance[""]
 
@@ -312,3 +312,8 @@ def test_default_importance_not_implemented(self):
         prob.print_in_data_block["imp"] = True
         with pytest.raises(NotImplementedError):
             prob.write_problem(io.StringIO())
+
+    def test_default_cell_importance(self):
+        """Test that new cells have default importance of 1.0 (Issue #735)"""
+        cell = montepy.Cell()
+        assert cell.importance.neutron == 1.0