流畅的python 第十章: 序列的修改、散列和切片

流畅的python 第十章: 序列的修改、散列和切片


python 魔术方法：__getitem__、__setitem__、__delitem__、__len__

可以通过__getitem__、__setitem__、__delitem__、__len__ 等方法使类拥有了通过下标来索引的能力。

>>> class Test:
	def __init__(self):
		self._dic = {};
	def __getitem__(self,key):
		return self._dic.get(key);
	def __setitem__(self,key,value):
		self._dic.setdefault(key,value)
	def __len__(self):
		return len(self._dic)
>>> 
>>> d = Test()
>>> d['name'] = 'zval'
>>> d
<__main__.Test object at 0x041938B0>
>>> d['age'] = 100
>>> d['name']
'zval'
>>> d['age']
100

__getattr_  __setattr__像访问类属性一样访问dict中的键值对。

>>> class Adict(dict):
	def __init__(self,indict={}):
		dict.__init__(self,indict)
	def __getattr__(self,item):
		try:
			return self.__getitem__(item)
		except KeyError:
			pass
		return None
	def __setattr__(self,item, value):
		return dict.__setattr__(self, item, value)

>>> d = Adict()
>>> d.name = 'zval'
>>> d.age=100
>>> d
{}
>>> d.name
'zval'
>>> d.age
100
>>>