'get_poly' returns None if (row, col) entry is empty, instead of raising a KeyError exception

1 files changed, 6 insertions, 4 deletions

diff --git a/polymatrix/expression/mixins/substituteexprmixin.py b/polymatrix/expression/mixins/substituteexprmixin.py
index 1ba8a1a..9741897 100644
--- a/polymatrix/expression/mixins/substituteexprmixin.py
+++ b/polymatrix/expression/mixins/substituteexprmixin.py
@@ -50,6 +50,9 @@ class SubstituteExprMixin(ExpressionBaseMixin):
             elif isinstance(substitution_expr, int) or isinstance(substitution_expr, float):
                 polynomial = {tuple(): substitution_expr}
 
+            else:
+                raise Exception(f'{substitution_expr=} not recognized')
+
             return state, result + (polynomial,)
 
         *_, (state, substitutions) = tuple(itertools.accumulate(
@@ -63,14 +66,13 @@ class SubstituteExprMixin(ExpressionBaseMixin):
         for row in range(underlying.shape[0]):
             for col in range(underlying.shape[1]):
             
-                try:
-                    underlying_terms = underlying.get_poly(row, col)
-                except KeyError:
+                polynomial = underlying.get_poly(row, col)
+                if polynomial is None:
                     continue
 
                 terms_row_col = collections.defaultdict(float)
 
-                for monomial, value in underlying_terms.items():
+                for monomial, value in polynomial.items():
 
                     terms_monomial = {tuple(): value}