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72 lines
2.5 KiB
Python
72 lines
2.5 KiB
Python
# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
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# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
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#
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# This file is part of logilab-common.
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#
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# logilab-common is free software: you can redistribute it and/or modify it under
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# the terms of the GNU Lesser General Public License as published by the Free
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# Software Foundation, either version 2.1 of the License, or (at your option) any
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# later version.
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#
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# logilab-common is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Lesser General Public License along
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# with logilab-common. If not, see <http://www.gnu.org/licenses/>.
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"""Bases class for interfaces to provide 'light' interface handling.
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TODO:
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_ implements a check method which check that an object implements the
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interface
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_ Attribute objects
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This module requires at least python 2.2
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"""
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__docformat__ = "restructuredtext en"
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class Interface(object):
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"""Base class for interfaces."""
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def is_implemented_by(cls, instance):
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return implements(instance, cls)
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is_implemented_by = classmethod(is_implemented_by)
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def implements(obj, interface):
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"""Return true if the give object (maybe an instance or class) implements
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the interface.
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"""
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kimplements = getattr(obj, '__implements__', ())
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if not isinstance(kimplements, (list, tuple)):
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kimplements = (kimplements,)
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for implementedinterface in kimplements:
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if issubclass(implementedinterface, interface):
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return True
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return False
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def extend(klass, interface, _recurs=False):
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"""Add interface to klass'__implements__ if not already implemented in.
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If klass is subclassed, ensure subclasses __implements__ it as well.
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NOTE: klass should be e new class.
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"""
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if not implements(klass, interface):
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try:
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kimplements = klass.__implements__
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kimplementsklass = type(kimplements)
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kimplements = list(kimplements)
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except AttributeError:
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kimplementsklass = tuple
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kimplements = []
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kimplements.append(interface)
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klass.__implements__ = kimplementsklass(kimplements)
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for subklass in klass.__subclasses__():
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extend(subklass, interface, _recurs=True)
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elif _recurs:
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for subklass in klass.__subclasses__():
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extend(subklass, interface, _recurs=True)
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