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#!/usr/bin/env python2
# Terminator by Chris Jones <cmsj@tenshu.net>
# GPL v2 only
"""borg.py - We are the borg. Resistance is futile.
http://code.activestate.com/recipes/66531/
ActiveState's policy appears to be that snippets
exist to encourage re-use, but I can not find any
specific licencing terms.
"""
from util import dbg
# pylint: disable-msg=R0903
# pylint: disable-msg=R0921
class Borg:
"""Definition of a class that can never be duplicated. Correct usage is
thus:
>>> from borg import Borg
>>> class foo(Borg):
... # All attributes on a borg class *must* = None
... attribute = None
... def __init__(self):
... Borg.__init__(self, self.__class__.__name__)
... def prepare_attributes(self):
... if not self.attribute:
... self.attribute = []
...
>>> bar = foo()
>>> bar.prepare_attributes()
The important thing to note is that all attributes of borg classes *must* be
declared as being None. If you attempt to use static class attributes you
will get unpredicted behaviour. Instead, prepare_attributes() must be called
which will then see the attributes in the shared state, and initialise them
if necessary."""
__shared_state = {}
def __init__(self, borgtype=None):
"""Class initialiser. Overwrite our class dictionary with the shared
state. This makes us identical to every other instance of this class
type."""
if borgtype is None:
raise TypeError('Borg::__init__: You must pass a borgtype')
if not self.__shared_state.has_key(borgtype):
dbg('Borg::__init__: Preparing borg state for %s' % borgtype)
self.__shared_state[borgtype] = {}
self.__dict__ = self.__shared_state[borgtype]
def prepare_attributes(self):
"""This should be used to prepare any attributes of the borg class."""
raise NotImplementedError('prepare_attributes')
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