manifold/util/frozendict.py

   1 import copy
   2
   3 class frozendict(dict):
   4     def _blocked_attribute(obj):
   5         raise AttributeError, "A frozendict cannot be modified."
   6     _blocked_attribute = property(_blocked_attribute)
   7
   8     __delitem__ = __setitem__ = clear = _blocked_attribute
   9     pop = popitem = setdefault = update = _blocked_attribute
  10
  11     def __new__(cls, *args, **kw):
  12         new = dict.__new__(cls)
  13
  14         args_ = []
  15         for arg in args:
  16             if isinstance(arg, dict):
  17                 arg = copy.copy(arg)
  18                 for k, v in arg.items():
  19                     if isinstance(v, dict):
  20                         arg[k] = frozendict(v)
  21                     elif isinstance(v, list):
  22                         v_ = list()
  23                         for elm in v:
  24                             if isinstance(elm, dict):
  25                                 v_.append( frozendict(elm) )
  26                             else:
  27                                 v_.append( elm )
  28                         arg[k] = tuple(v_)
  29                 args_.append( arg )
  30             else:
  31                 args_.append( arg )
  32
  33         dict.__init__(new, *args_, **kw)
  34         return new
  35
  36     def __init__(self, *args, **kw):
  37         pass
  38
  39     def __hash__(self):
  40         try:
  41             return self._cached_hash
  42         except AttributeError:
  43             h = self._cached_hash = hash(tuple(sorted(self.items())))
  44             return h
  45
  46     def __repr__(self):
  47         return "frozendict(%s)" % dict.__repr__(self)