Fix error message for boolean operator on symbols (#3765)

* Fix error message for boolean operator on symbols * style: pre-commit fixes --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Arjun <[email protected]>
pybamm-team · Jan 25, 2024 · a3a3746 · a3a3746
1 parent 00916f3
commit a3a3746
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/pybamm/expression_tree/symbol.py b/pybamm/expression_tree/symbol.py
@@ -670,7 +670,16 @@ def __mod__(self, other):
         return pybamm.simplify_if_constant(pybamm.Modulo(self, other))
 
     def __bool__(self):
-        raise NotImplementedError("Boolean operator not defined for Symbols.")
+        raise NotImplementedError(
+            "Boolean operator not defined for Symbols. You might be seeing this message because you are trying to "
+            "specify an if statement based on the value of a symbol, e.g."
+            "\nif x < 0:\n"
+            "\ty = 1\n"
+            "else:\n"
+            "\ty = 2\n"
+            "In this case, use heaviside functions instead:"
+            "\ny = 1 * (x < 0) + 2 * (x >= 0)"
+        )
 
     def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
         """