Updated abstract.py example.

examples/abstract.py

@@ -3,25 +3,26 @@
 from abc import ABCMeta, abstractmethod
 from simplestruct import Struct, Field, MetaStruct
 
+
+# A simple ABC. Subclasses must provide an override for foo().
 class Abstract(metaclass=ABCMeta):
     @abstractmethod
     def foo(self):
         pass
 
-# If we ran this code
-#
-#     class Concrete(Abstract, Struct):
-#         f = Field
-#         def foo(self):
-#             return self.f ** 2
-#
-# we would get the following error:
-#
-#     TypeError: metaclass conflict: the metaclass of a derived class
-#     must be a (non-strict) subclass of the metaclasses of all its bases
-#
-# So let's make a trivial subclass of ABCMeta and MetaStruct.
+# ABCs rely on a metaclass that conflicts with Struct's metaclass.
+try:
+    class Concrete(Abstract, Struct):
+        f = Field
+        def foo(self):
+            return self.f ** 2
+
+except TypeError as e:
+    print(e)
+    # metaclass conflict: the metaclass of a derived class must
+    # be a (non-strict) subclass of the metaclasses of all its bases
 
+# So let's make a trivial subclass of ABCMeta and MetaStruct.
 class ABCMetaStruct(MetaStruct, ABCMeta):
     pass
 
@@ -33,13 +34,13 @@ def foo(self):
 c = Concrete(5)
 print(c.foo())      # 25
 
-# For convenience we can also do
 
+# For convenience we can make a version of Struct that
+# incorporates the common metaclass.
 class ABCStruct(Struct, metaclass=ABCMetaStruct):
     pass
 
-# and then
-
+# Now we only have to do:
 class Concrete(Abstract, ABCStruct):
     f = Field
     def foo(self):