ex 7.4

structure.py

@@ -39,3 +39,8 @@ class Structure:
         locs = {}
         exec(code, locs)
         cls.__init__ = locs['__init__']
+
+
+def typed_structure(clsname, **validators):
+    cls = type(clsname, (Structure,), validators)
+    return cls

validate.py

@@ -27,16 +27,14 @@ class Typed(Validator):
         return super().check(value)
 
 
-class Integer(Typed):
-    expected_type = int
+_typed_classes = [
+    ('Integer', 'int'),
+    ('Float', 'float'),
+    ('String', 'str'),
+]
 
-
-class Float(Typed):
-    expected_type = float
-
-
-class String(Typed):
-    expected_type = str
+globals().update((name, type(name, (Typed,), {'expected_type': ty}))
+                 for name, ty in _typed_classes)
 
 
 class Positive(Validator):