logger handles exception

src/fancymath/__main__.py

@@ -33,4 +33,7 @@ logger.info(f"{v1=}")
 logger.info(f"{v2=}")
 logger.info(f"{v3=}")
 
-v4 = v2.dot([1,2,3])
+try:
+    v4 = v2.dot([1,2,3])
+except ValueError as err:
+    logger.exception(err)

src/fancymath/vector.py

@@ -16,8 +16,8 @@ class Vector(object):
     def dot(self, v):
         """Returns the dot product with Vector *v*."""
         if not isinstance(v, self.__class__):
-            logger.error(f"Expected an instance of {self.__class__}, but got {type(v)} instead.")
+            msg = f"Expected an instance of {self.__class__}, but got {type(v)} instead."
-            return None
+            raise ValueError(msg)
         d = self.x * v.x + self.y * v.y + self.z * v.z
         return d