强大如斯的Bunch类

该类构造如下： 

class Bunch(dict):
    """Container object for datasets

    Dictionary-like object that exposes its keys as attributes.

    >>> b = Bunch(a=1, b=2)
    >>> b['b']
    2
    >>> b.b
    2
    >>> b.a = 3
    >>> b['a']
    3
    >>> b.c = 6
    >>> b['c']
    6

    """

    def __init__(self, **kwargs):
        super(Bunch, self).__init__(kwargs)

    def __setattr__(self, key, value):
        self[key] = value

    def __dir__(self):
        return self.keys()

    def __getattr__(self, key):
        try:
            return self[key]
        except KeyError:
            raise AttributeError(key)

    def __setstate__(self, state):
        # Bunch pickles generated with scikit-learn 0.16.* have an non
        # empty __dict__. This causes a surprising behaviour when
        # loading these pickles scikit-learn 0.17: reading bunch.key
        # uses __dict__ but assigning to bunch.key use __setattr__ and
        # only changes bunch['key']. More details can be found at:
        # https://github.com/scikit-learn/scikit-learn/issues/6196.
        # Overriding __setstate__ to be a noop has the effect of
        # ignoring the pickled __dict__
        pass

obj.var原理是什么呢？

实践方案：注释掉 __setattr__，在__getattr__中打印信息

class Bunch(dict):
    """Container object for datasets

    Dictionary-like object that exposes its keys as attributes.

    >>> b = Bunch(a=1, b=2)
    >>> b['b']
    2
    >>> b.b
    2
    >>> b.a = 3
    >>> b['a']
    3
    >>> b.c = 6
    >>> b['c']
    6

    """

    def __init__(self, **kwargs):
        print("init start")
        super(Bunch, self).__init__(kwargs)
        print("init end")
        
    """
    def __setattr__(self, key, value):
        print("setattr init",key,value)
        self[key] = value
        print("setattr end",key,value)
    """
    
    def __dir__(self):
        return self.keys()

    def __getattr__(self, key):
        print("get key:{0}".format(key))
        try:
            return self[key]
        except KeyError:
            raise AttributeError(key)

    def __setstate__(self, state):
        # Bunch pickles generated with scikit-learn 0.16.* have an non
        # empty __dict__. This causes a surprising behaviour when
        # loading these pickles scikit-learn 0.17: reading bunch.key
        # uses __dict__ but assigning to bunch.key use __setattr__ and
        # only changes bunch['key']. More details can be found at:
        # https://github.com/scikit-learn/scikit-learn/issues/6196.
        # Overriding __setstate__ to be a noop has the effect of
        # ignoring the pickled __dict__
        pass

b = Bunch(a=1, b=2)
b.a
b.b

init start
init end
get key:a
get key:b

上面可以证明是__getattr__的作用

今天的文章强大如斯的Bunch类分享到此就结束了，感谢您的阅读。