Source code for zope.annotation.attribute
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Attribute Annotations implementation"""
import logging
from collections.abc import MutableMapping as DictMixin
try:
from BTrees.OOBTree import OOBTree as _STORAGE
except ImportError: # pragma: no cover
logging.getLogger(__name__).warning(
'BTrees not available: falling back to dict for attribute storage')
_STORAGE = dict
from zope import component
from zope import interface
from zope.annotation import interfaces
_EMPTY_STORAGE = _STORAGE()
[docs]
@interface.implementer(interfaces.IAnnotations)
@component.adapter(interfaces.IAttributeAnnotatable)
class AttributeAnnotations(DictMixin):
"""Store annotations on an object
Store annotations in the `__annotations__` attribute on a
`IAttributeAnnotatable` object.
"""
# Yes, there's a lot of repetition of the `getattr` call,
# but that turns out to be the most efficient for the ways
# instances are typically used without sacrificing any semantics.
# See https://github.com/zopefoundation/zope.annotation/issues/8
# for a discussion of alternatives (which included functools.partial,
# a closure, capturing the annotations in __init__, and versions
# with getattr and exceptions).
def __init__(self, obj, context=None):
self.obj = obj
@property
def __parent__(self):
return self.obj
def __bool__(self):
return bool(getattr(self.obj, '__annotations__', 0))
def get(self, key, default=None):
"""See zope.annotation.interfaces.IAnnotations"""
annotations = getattr(self.obj, '__annotations__', _EMPTY_STORAGE)
return annotations.get(key, default)
def __getitem__(self, key):
annotations = getattr(self.obj, '__annotations__', _EMPTY_STORAGE)
return annotations[key]
def keys(self):
annotations = getattr(self.obj, '__annotations__', _EMPTY_STORAGE)
return annotations.keys()
def __iter__(self):
annotations = getattr(self.obj, '__annotations__', _EMPTY_STORAGE)
return iter(annotations)
def __len__(self):
annotations = getattr(self.obj, '__annotations__', _EMPTY_STORAGE)
return len(annotations)
def __setitem__(self, key, value):
"""See zope.annotation.interfaces.IAnnotations"""
try:
annotations = self.obj.__annotations__
except AttributeError:
annotations = self.obj.__annotations__ = _STORAGE()
annotations[key] = value
def __delitem__(self, key):
"""See zope.app.interfaces.annotation.IAnnotations"""
try:
annotation = self.obj.__annotations__
except AttributeError:
raise KeyError(key)
del annotation[key]