HashableFunc.py

class HashableFunc(object):
  """
  This class acts as a decorator to make a function persistently hashable
  """
  
  relevant_attr_names = ['co_argcount', 'co_cellvars', 'co_code', 'co_consts', 
           'co_filename', 'co_firstlineno', 'co_flags', 'co_freevars',
           'co_lnotab', 'co_name', 'co_names', 'co_nlocals', 'co_stacksize',
           'co_varnames']

  def relevent_attrs(self):
    return tuple(getattr(func.__code__,s) for s in relevant_attr_names)

  def __init__(self, func):
    self.func = func

  def __hash__(self):
    return hash(self.relevant_attrs())

  def __call__(self, *args, **kwargs):
    return self.func(*args, **kwargs)

  def __eq__(self, other):
    return self.relevant_attrs() == other.relevant_attrs

@HashableFunc
def fib(a):
  if a <= 1:
    return 1
  return fib(a-1) + fib(a-2)