add logging and main function to fancymath

src/fancymath/vector.py

@@ -1,8 +1,11 @@
 """This module defines the Vector class. """
-
+import logging
 from math import acos, sqrt
 
 
+logger = logging.getLogger(__name__)
+
+
 class Vector(object):
     def __init__(self, x, y, z):
         """Constructor method."""
@@ -12,6 +15,9 @@ 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.")
+            return None
         d = self.x * v.x + self.y * v.y + self.z * v.z
         return d