immutable dictionary - Python 3.x

 Frozendict is an immutable wrapper around dictionaries that implements the
 complete mapping interface. It can be used as a drop-in replacement for
 dictionaries where immutability is desired.
 .
 Of course, this is Python, and you can still poke around the object's
 internals if you want.
 .
 The frozendict constructor mimics dict, and all of the expected interfaces
 (iter, len, repr, hash, getitem) are provided. Note that a frozendict does not
 guarantee the immutability of its values, so the utility of hash method is
 restricted by usage.
 .
 The only difference is that the copy() method of frozendict takes variable
 keyword arguments, which will be present as key/value pairs in the new,
 immutable copy.
 .
 This package contains the Python 3.x module.