python/Tools/frozendict.py

0001 # frozendict clas, from http://code.activestate.com/recipes/414283-frozen-dictionaries/
0002
0003 import copy
0004
0005 class frozendict(dict):
0006     def _blocked_attribute(obj):
0007         raise AttributeError("A frozendict cannot be modified.")
0008     _blocked_attribute = property(_blocked_attribute)
0009
0010     __delitem__ = __setitem__ = clear = _blocked_attribute
0011     pop = popitem = setdefault = update = _blocked_attribute
0012
0013     def __new__(cls, *args, **kw):
0014         new = dict.__new__(cls)
0015
0016         args_ = []
0017         for arg in args:
0018             if isinstance(arg, dict):
0019                 arg = copy.copy(arg)
0020                 for k, v in arg.items():
0021                     if isinstance(v, dict):
0022                         arg[k] = frozendict(v)
0023                     elif isinstance(v, list):
0024                         v_ = list()
0025                         for elm in v:
0026                             if isinstance(elm, dict):
0027                                 v_.append( frozendict(elm) )
0028                             else:
0029                                 v_.append( elm )
0030                         arg[k] = tuple(v_)
0031                 args_.append( arg )
0032             else:
0033                 args_.append( arg )
0034
0035         dict.__init__(new, *args_, **kw)
0036         return new
0037
0038     def __init__(self, *args, **kw):
0039         pass
0040
0041     def __hash__(self):
0042         try:
0043             return self._cached_hash
0044         except AttributeError:
0045             h = self._cached_hash = hash(frozenset(self.items()))
0046             return h
0047
0048     def __repr__(self):
0049         return "frozendict(%s)" % dict.__repr__(self)
0050