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