定义一个可以通过属性访问的字典

In [6]: class attrdict(dict):
...:        def __getattr__(self, attr):
...:            try:
...:                return self[attr]
...:            except KeyError:
...:                raise AttributeError(attr)
...:

In [7]: op = attrdict(AND='and',OR='or')

In [8]: op
Out[8]: {'AND': 'and', 'OR': 'or'}

In [9]: op.AND
Out[9]: 'and'

In [10]: op.OR
Out[10]: 'or'

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Ref:
1.来自peewee源码