python property

python property() 函数用于返回 property 属性
通常用来 建立和管理 class attribute

class property(fget=None, fset=None, fdel=None, doc=None)
Return a property attribute.
fget is a function for getting an attribute value. 
fset is a function for setting an attribute value. 
fdel is a function for deleting an attribute value. 
And doc creates a docstring for the attribute.

为一个类添加 property属性

class Person:
    def __init__(self):
        self._name = None
    def get_name(self):
        print('get_name called')
        return self._name
    def set_name(self, i):
        print('set_name called')
        self._name = i
    def del_name(self):
        print('del_name called')
        del self._name
    name = property(get_name, set_name, del_name, "Person's Name Attribute")
d = Person()
d.name = 'Pankaj'
print(d.name)
del d.name
'''
class Person:
    def __init__(self):
        self._name = None
    def get_name(self):
        print('get_name called')
        return self._name
    def set_name(self, i):
        print('set_name called')
        self._name = i
    def del_name(self):
        print('del_name called')
        del self._name
    name = property(get_name, set_name, del_name, "Person's Name Attribute")
d = Person()
d.name = 'Pankaj'
print(d.name)
del d.name
'''

注意： Person name property 是通过指定的方法管理的，实际属性为 Person 的私有属性 _name
我们可以建立 只读属性或者 non-deletable attribute。

# non-delete 
name = property(get_name, set_name, None)
# read-only
name = property(get_name, None, None)

基于 装饰器，python 提供了 property 的简写

class Data:
    def __init__(self):
        self._id = None
    @property
    def id(self):
        print('id getter')
        return self._id
    @id.setter
    def id(self, i):
        print('id setter')
        self._id = i
    @id.deleter
    def id(self):
        print('id deleter')
        del self._id
d = Data()
d.id = 100
print(d.id)
del d.id