41 lines
996 B
Python
41 lines
996 B
Python
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# Copyright 2013 Eygene A. Ryabinkin.
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#
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# Collection of classes that implement const-like behaviour
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# for various objects.
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import copy
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class ConstProxy (object):
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"""
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Implements read-only access to a given object
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that can be attached to each instance only once.
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"""
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def __init__ (self):
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self.__dict__['__source'] = None
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def __getattr__ (self, name):
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src = self.__dict__['__source']
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if src == None:
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raise ValueError ("using non-initialized ConstProxy() object")
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return copy.deepcopy (getattr (src, name))
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def __setattr__ (self, name, value):
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raise AttributeError ("tried to set '%s' to '%s' for constant object" % \
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(name, value))
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def __delattr__ (self, name):
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raise RuntimeError ("tried to delete field '%s' from constant object" % \
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(name))
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def set_source (self, source):
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""" Sets source object for this instance. """
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if (self.__dict__['__source'] != None):
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raise ValueError ("source object is already set")
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self.__dict__['__source'] = source
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