Immutable record like objects that just hold a bunch of data and stay immutable for the forseeable future

immutability.py

#!/usr/bin/env python
# encoding: utf-8

from __future__ import print_function

class ImmutabilityException(BaseException):
    pass

class ImmutableRecord(object):

    def __init__(self, **kwargs):
        self._record = kwargs
        for name, value in kwargs.items():
            setattr(self, name, value)
        self._immutable = True

    def __setattr__(self, name, value):
        if hasattr(self, '_immutable') and self._immutable:
            raise ImmutabilityException('Unable to modify {name} in immutable record object'.format(name=name))
        return super(ImmutableRecord, self).__setattr__(name, value)

    def set(self, **kwargs):
        new_record = dict(self._record)
        new_record.update(kwargs)
        return self.__class__(**new_record)

class Person(ImmutableRecord):

    def __init__(self, name, sex):
        super(Person, self).__init__(name=name, sex=sex)

    def __str__(self):
        return '<Person name={name} sex={sex}>'.format(name=self.name, sex=self.sex)

jack = Person(name='Jack', sex='m')
print(jack) # <Person name=Jack sex=m>
jill = jack.set(name='Jill')
print(jack) # <Person name=Jack sex=m>
print(jill) # <Person name=Jill sex=m>

As it turns out, I have a problem with understanding the "batteries included" philosophy of python!
http://docs.python.org/library/collections.html#collections.namedtuple