Merge pull request #2141 from pybamm-team/issue-2115-bool

#2115 Boolean operator not implemented

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ## Bug fixes
 
+-   Raise explicit `NotImplementedError` if trying to call `bool()` on a pybamm Symbol (e.g. in an if statement condition) ([#2141](https://github.com/pybamm-team/PyBaMM/pull/2141))
 -   Fixed bug causing cut-off voltage to change after setting up a simulation with a model ([#2138](https://github.com/pybamm-team/PyBaMM/pull/2138))
 -   A single solution cycle can now be used as a starting solution for a simulation ([#2138](https://github.com/pybamm-team/PyBaMM/pull/2138))
 

pybamm/expression_tree/functions.py

@@ -84,7 +84,7 @@ def diff(self, variable):
                     ) * child.diff(variable)
 
             # remove None entries
-            partial_derivatives = list(filter(None, partial_derivatives))
+            partial_derivatives = [x for x in partial_derivatives if x is not None]
 
             derivative = sum(partial_derivatives)
             if derivative == 0:

pybamm/expression_tree/symbol.py

@@ -656,6 +656,9 @@ def __mod__(self, other):
         """return an :class:`Modulo` object."""
         return pybamm.simplify_if_constant(pybamm.Modulo(self, other))
 
+    def __bool__(self):
+        raise NotImplementedError("Boolean operator not defined for Symbols.")
+
     def diff(self, variable):
         """
         Differentiate a symbol with respect to a variable. For any symbol that can be

pybamm/models/base_model.py

@@ -746,7 +746,7 @@ def info(self, symbol_name):
         div = "-----------------------------------------"
         symbol = find_symbol_in_model(self, symbol_name)
 
-        if not symbol:
+        if symbol is None:
             return None
 
         print(div)
@@ -1034,22 +1034,22 @@ def find_symbol_in_tree(tree, name):
     elif len(tree.children) > 0:
         for child in tree.children:
             child_return = find_symbol_in_tree(child, name)
-            if child_return:
+            if child_return is not None:
                 return child_return
 
 
 def find_symbol_in_dict(dic, name):
     for tree in dic.values():
         tree_return = find_symbol_in_tree(tree, name)
-        if tree_return:
+        if tree_return is not None:
             return tree_return
 
 
 def find_symbol_in_model(model, name):
     dics = [model.rhs, model.algebraic, model.variables]
     for dic in dics:
         dic_return = find_symbol_in_dict(dic, name)
-        if dic_return:
+        if dic_return is not None:
             return dic_return
 
 

pybamm/models/submodels/particle/base_particle.py

@@ -39,16 +39,20 @@ def _get_standard_concentration_variables(
 
         # Get surface concentration if not provided as fundamental variable to
         # solve for
-        c_s_surf = c_s_surf or pybamm.surf(c_s)
+        if c_s_surf is None:
+            c_s_surf = pybamm.surf(c_s)
         c_s_surf_av = pybamm.x_average(c_s_surf)
 
         c_scale = self.domain_param.c_max
 
         # Get average concentration(s) if not provided as fundamental variable to
         # solve for
-        c_s_xav = c_s_xav or pybamm.x_average(c_s)
-        c_s_rav = c_s_rav or pybamm.r_average(c_s)
-        c_s_av = c_s_av or pybamm.r_average(c_s_xav)
+        if c_s_xav is None:
+            c_s_xav = pybamm.x_average(c_s)
+        if c_s_rav is None:
+            c_s_rav = pybamm.r_average(c_s)
+        if c_s_av is None:
+            c_s_av = pybamm.r_average(c_s_xav)
 
         variables = {
             self.domain + " particle concentration": c_s,

tests/unit/test_expression_tree/test_symbol.py

@@ -495,6 +495,15 @@ def test_is_matrix_zero(self):
         self.assertFalse(pybamm.is_matrix_zero(b))
         self.assertFalse(pybamm.is_matrix_zero(c))
 
+    def test_bool(self):
+        a = pybamm.Symbol("a")
+        with self.assertRaisesRegex(NotImplementedError, "Boolean"):
+            bool(a)
+        # if statement calls Boolean
+        with self.assertRaisesRegex(NotImplementedError, "Boolean"):
+            if a > 1:
+                print("a is greater than 1")
+
 
 if __name__ == "__main__":
     print("Add -v for more debug output")