@property
class Animal(object):

    def __init__(self, name, age):
        self._name = name
        self._age = age
        self._color = 'Black'

    @property
    def name(self):
        return self._name

    @name.setter
    def name(self, value):
        if isinstance(value, basestring):
            self._name = value
        else:
            self._name = 'No name'

    @property
    def age(self):
        return self._age

    @age.setter
    def age(self, value):
        if value > 0 and value < 100:
            self._age = value
        else:
            self._age = 0
            # print 'invalid age value.'

    @property
    def color(self):
        return self._color

    @color.setter
    def color(self, value):
        self._color = value;
    
a = Animal('black dog', 3)
a.name = 'white dog'
a.age = 300
print 'Name:', a.name
print 'Age:', a.age
 

property函式
它以一個函式形式，定義一個屬性，與@property實現原理類似，或者就是它的的變異用法。
其原型為：

property(fget=None, fset=None, fdel=None, doc=None)

1. class Animal(object):
       def __init__(self, name, age):
           self._name = name
           self._age = age
           self._color = 'Black'
   
       def get_name(self):
           return self._name
   
       def set_name(self, value):
           if isinstance(value, basestring):
               self._name = value
           else:
               self._name = 'No name'
   
       name = property(fget=get_name, fset=set_name, fdel=None, doc='name of an animal')
   
       def get_age(self):
           return self._age
   
       def set_age(self, value):
           if value > 0 and value < 100:
               self._age = value
           else:
               self._age = 0
               # print 'invalid age value.'
   
       age = property(fget=get_age, fset=set_age, fdel=None, doc='name of an animal')
       
   
   a = Animal('black dog', 3)
   a.name = 'white dog'
   a.age = 3
   print 'Name:', a.name
   print Animal.name.__doc__
   print 'Age:', a.age