devel/py-frozendict - The NetBSD Packages Collection

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.