immutable decorator

immutable.py

import functools

def make_immutable(obj):
    """Tries to create an immutable version of an object

    Converts object into a nested structure of named tuples where possible.
    Primative types (int, str, float, bool) are unchanged but lists and sets are
    converted into tuples. Objects are converted into named tuples.

    This is not a terribly sophisticated function and will work best with
    objects that contain simple types of data.

    Arguments:
        obj - the object to convert

    Returns:
        a namedtuple of the same name as the class of the object pass in

    """
    if isinstance(obj, (list, tuple, set)):
        return tuple(make_immutable(v) for v in obj)

    if type(obj) in (int, str, float, bool):
        return obj 

    try:
        name = obj.__class__.__name__
        attrs = {}
        for key, val in obj.__dict__.items():
            value = make_immutable(val)
            if value is not None:
                attrs[key] = value

        return collections.namedtuple(name, attrs.keys())(**attrs)
    except (AttributeError, TypeError):
        pass

    return None


def immutable(f):
    """Decorator that makes return value immutable"""
    @functools.wraps(f)
    def impl(*args, **kwargs):
        return make_immutable(f(*args, **kwargs))

    return impl