AppPkg/Applications/Python/Python-2.7.2/Demo/metaclasses/Simple.py

   1 import types
   2
   3 class Tracing:
   4     def __init__(self, name, bases, namespace):
   5         """Create a new class."""
   6         self.__name__ = name
   7         self.__bases__ = bases
   8         self.__namespace__ = namespace
   9     def __call__(self):
  10         """Create a new instance."""
  11         return Instance(self)
  12
  13 class Instance:
  14     def __init__(self, klass):
  15         self.__klass__ = klass
  16     def __getattr__(self, name):
  17         try:
  18             value = self.__klass__.__namespace__[name]
  19         except KeyError:
  20             raise AttributeError, name
  21         if type(value) is not types.FunctionType:
  22             return value
  23         return BoundMethod(value, self)
  24
  25 class BoundMethod:
  26     def __init__(self, function, instance):
  27         self.function = function
  28         self.instance = instance
  29     def __call__(self, *args):
  30         print "calling", self.function, "for", self.instance, "with", args
  31         return apply(self.function, (self.instance,) + args)
  32
  33 Trace = Tracing('Trace', (), {})
  34
  35 class MyTracedClass(Trace):
  36     def method1(self, a):
  37         self.a = a
  38     def method2(self):
  39         return self.a
  40
  41 aninstance = MyTracedClass()
  42
  43 aninstance.method1(10)
  44
  45 print aninstance.method2()