py: Freeze a nested dict, tuple and/or list. Used to check whether a given state has changed.

freeze.py

def freeze(obj):
    """
    """
    def _freeze(obj):
        def do_list():
            for i in obj:
                yield _freeze(i)

        def do_dict():
            for k, v in obj.items():
                yield k, _freeze(v)

        if isinstance(obj, tuple):
            return tuple(do_list())

        elif isinstance(obj, list):
            return tuple(do_list())

        elif isinstance(obj, dict):
            return tuple(sorted(dict(do_dict()).items()))

        else:
            return obj

    return frozenset(_freeze(obj))