python 对象的属性

python 对象的属性

1

[root@dev test]# cat a.py       
#!/usr/bin/env python

class Bird(object):
    feather = True

class Chicken(Bird):
    fly = False
    def __init__(self,age):
        self.age = age

chick = Chicken(2)

print(Bird.__dict__)      #查看类属性
print(Chicken.__dict__)   #查看子类属性
print(chick.__dict__)     #查看对象属性
print('-------------------')
chick.__dict__['age'] = 3
print(chick.__dict__['age'])
chick.age = 10
print(chick.age)

[root@dev test]# python a.py
{'__dict__': <attribute '__dict__' of 'Bird' objects>, '__module__': '__main__', '__weakref__': <attribute '__weakref__' of 'Bird' objects>, 'feather': True, '__doc__': None}
{'fly': False, '__module__': '__main__', '__doc__': None, '__init__': <function __init__ at 0x7f9bce427758>}
{'age': 2}
-------------------
3
10

# 特性,是特殊的属性,使用property声明,可以传入四个参数
[root@dev test]# cat b.py
#!/usr/bin/env python
class num(object):
    def __init__(self,value):
        self.value = value
    def getNeg(self):
        return -self.value
    def setNeg(self,value):
        self.value = -value
    def delNeg(self):
        print('value also deleted')
        del self.value
    neg = property(getNeg,setNeg,delNeg,"I'm negative")

x = num(1.1)
print(x.neg)

x.neg = -22
print(x.value)
print(num.neg.__doc__)
del x.neg

[root@dev test]# python b.py
-1.1
22
I'm negative
value also deleted


[root@dev test]# cat c.py
#!/usr/bin/env python
class bird(object):
    feather = True
class chicken(bird):
    fly = False
    def __init__(self,age):
        self.age = age
    def __getattr__(self,name):
        if name == 'adult':
            if self.age > 1.0:
                return True
            else:
                return False
        else:
            raise AttributeError(name)
summer = chicken(2)
print(summer.adult)
summer.age = 0.5
print(summer.adult)
print(summer.male)

[root@dev test]# python c.py
True
False
Traceback (most recent call last):
  File "c.py", line 29, in <module>
    print(summer.male)
  File "c.py", line 19, in __getattr__
    raise AttributeError(name)
AttributeError: male