Python类作为数据存储区

Question

我正在尝试编写一个类似于某种数据存储区的Python类.因此,我不想使用字典,而是希望以class.foo的形式访问我的数据,并且仍然可以执行所有很酷的操作,例如迭代它,就像数据类中的x一样.

以下是我提出的:

class MyStore(object):
    def __init__(self, data):
        self._data = {}
        for d in data:
            # Just for the sake of example
            self._data[d] = d.upper()

    def __iter__(self):
        return self._data.values().__iter__()

    def __len__(self):
        return len(self._data)

    def __contains__(self, name):
        return name in self._data

    def __getitem__(self, name):
        return self._data[name]

    def __getattr__(self, name):
        return self._data[name]


store = MyStore(['foo', 'bar', 'spam', 'eggs'])
print "Store items:", [item for item in store]
print "Number of items:", len(store)
print "Get item:", store['foo']
print "Get attribute:", store.foo
print "'foo' is in store:", 'foo' in store

并且,显然它有效.万岁!但是如何正确实现属性的设置呢？添加以下内容最终会在递归限制中__getattr__:

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

阅读文档,我应该调用超类(对象)__setattr__方法来避免递归,但这样我无法控制我的self._data dict.

有人能指出我正确的方向吗？

Answer 1

试试这个:

def __setattr__(self, name, value):
    super(MyStore, self).__setattr__(name, value)
    self._data[name] = value

但是,你可以通过继承类似下面的东西来节省很多麻烦dict:

class MyStore(dict):

    def __init__(self, data):
        for d in data:
            self[d] = d.upper()

    def __getattr__(self, name):
        return self[name]

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

store = MyStore(['foo', 'bar', 'spam', 'eggs'])
print "Store items:", [item for item in store]
print "Number of items:", len(store)
print "Get item:", store['foo']
print "Get attribute:", store.foo
print "'foo' is in store:", 'foo' in store
store.qux = 'QUX'
print "Get qux item:", store['qux']
print "Get qux attribute:", store.qux
print "'qux' is in store:", 'qux' in store

哪个输出......

Store items: ['eggs', 'foo', 'bar', 'spam']
Number of items: 4
Get item: FOO
Get attribute: FOO
'foo' is in store: True
Get qux item: QUX
Get qux attribute: QUX
'qux' is in store: True