Here's a frozendict with reference:
```
class frozendict(dict):
# from http://code.activestate.com/recipes/414283-frozen-dictionaries/
def _blocked_attribute(obj):
raise AttributeError("A frozendict cannot be modified.")
_blocked_attribute = property(_blocked_attribute)
__delitem__ = __setitem__ = clear = _blocked_attribute
pop = popitem = setdefault = update = _blocked_attribute
def __new__(cls, *args, **kw):
new = dict.__new__(cls)
args_ = []
for arg in args:
if isinstance(arg, dict):
arg = copy.copy(arg)
for k, v in arg.items():
if isinstance(v, dict):
arg[k] = frozendict(v)
elif isinstance(v, list):
v_ = list()
for elm in v:
if isinstance(elm, dict):
v_.append( frozendict(elm) )
else:
v_.append( elm )
arg[k] = tuple(v_)
args_.append( arg )
else:
args_.append( arg )
dict.__init__(new, *args_, **kw)
return new
def __init__(self, *args, **kw):
pass
def __hash__(self):
try:
return self._cached_hash
except AttributeError:
h = self._cached_hash = hash(frozenset(self.items()))
return h
def __repr__(self):
return "frozendict(%s)" % dict.__repr__(self)
```
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