字典的python对象样式访问；想不通

Question

class ObjectDict(dict):
    """ allows object style access for dictionaries """

    def __getattr__(self, name):
        if name in self:
            return self[name]
        else:
            raise AttributeError('No such attribute: %s' % name)

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

    def __delattr__(self, name):
        if name in self:
            del self[name]
        else:
            raise AttributeError('No such attribute: %s' % name)

有人可以为我解释一下这段代码吗？我只是一个python初学者。

Answer 1

ObjectDict 实例是通过类继承的常规字典。见ObjectDict(dict)

__getattr__ 魔术函数允许为任何对象定义点符号访问。它只是在这里调用普通的字典访问

同样，__setattr__ 和 __delattr__ 允许从点表示法设置和删除（使用 Python 的 del 表达式）值。但是，要设置嵌套值，您需要第一个键的值也是 ObjectDict

Answer 2

__getattr__ 用于获取数据。

__setattr__ 用于设置数据。

__delattr__ 适用于您想要删除数据的时候。

现在，方法应该很清楚了。

def __getattr__(self, name):
    # if the key exists... return it.
    if name in self:
        return self[name]
    # if not : raise an error.
    else:
        raise AttributeError('No such attribute: %s' % name)

def __setattr__(self, name, value):
    # set VALUE as value, with NAME as key in the dict.
    self[name] = value

def __delattr__(self, name):
    # if the key "name" exists in the dictionnary... delete it
    if name in self:
        del self[name]
    # else, it doesnt exist, so cant delete it.
    else:
        raise AttributeError('No such attribute: %s' % name)