bluechips/lib/subclass.py

   1 """
   2 Create subclasses that call out to their "superclass" for all methods
   3 but return the "subclass's" type
   4 """
   5
   6 from weakref import WeakValueDictionary
   7
   8 def wrapper(c, func):
   9     return (lambda self,*args: c(getattr(self.value, func)(*map(self.value.__class__, args))))
  10
  11 def __new__(cls, value=0):
  12     if value not in cls.__old_values__:
  13         new_object = super(cls, cls).__new__(cls, value)
  14         cls.__old_values__[value] = new_object
  15         return new_object
  16     else:
  17         return cls.__old_values__[value]
  18
  19 class SmartSubclass(object):
  20     def __init__(self, superclass, exclude=[]):
  21         self.superclass = superclass
  22         self.exclude = exclude
  23     def __call__(self, name, bases, dict):
  24         dict['__old_values__'] = WeakValueDictionary()
  25         dict['__new__'] = __new__
  26         c = type(name, bases, dict)
  27         for func in dir(self.superclass):
  28             if func not in dir(c) and \
  29                 callable(getattr(self.superclass, func)) and \
  30                 func not in self.exclude:
  31                 setattr(c, func, wrapper(c, func))
  32         return c
  33
  34 __all__ = ['SmartSubclass']