静态属性



In [5]:

    
class Person():
    age = 10

x = Person()

print(Person.age)  #静态变量可以直接用
print(x.age)

Person.age = 20    #直接更改静态变量会对其实例参数影响
print(x.age)

x.age = 30         #在实例中更改静态变量只会对实例内部的静态变量产生影响
print(Person.age)



In [6]:

    
class Person():
    @classmethod    #静态方法
    def method(self):
        print("hello")
Person.method()









    



hello

委托

在c#中委托是指指向某个函数的一个变量，事实上就是在某个对象中内嵌入其他对象，以实现请求的传递

在python中委托是通过getattr实现的



In [2]:

    
class wrapper:
    def __init__(self,object):
        self.wrapped = object
    def __getattr__(self,attrname):
        print("trace",attrname)
        return getattr(self.wrapped,attrname)
a = wrapper([1,2,3])
a.append(3)      #a.append(3)转化成 self.wrapped.append(3) 
a.wrapped        #getattr(X,N)会执行X.N









    



trace append






    Out[2]:





[1, 2, 3, 3]

伪私有属性



In [11]:

    
#使用伪私有属性主要是避免实例内部命名冲突
class c1:
    def meth1(self):
        self.x = 88
class c2:
    def metha(self):
        self.x = 99
class c3(c1,c2):
    pass
a = c3()
a.meth1()
a.metha()    #这里两个类中都有x这样就会出现冲突
print(a.x)



In [15]:

    
class c1:
    def meth1(self):
        self.__x = 88
class c2:
    def metha(self):
        self.__x = 99
class c3(c1,c2):
    pass
a = c3()
a.meth1()
a.metha()   #在这里，x会自动扩充为_c2__x和_c1__x
print(a._c2__x,a._c1__x)  #正常输出

print(a.x)  #报错









    



99 88






    



---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-15-6e0230393033> in <module>()
     12 print(a._c2__x,a._c1__x)  #正常输出
     13 
---> 14 print(a.x)  #报错

AttributeError: 'c3' object has no attribute 'x'

工厂类



In [16]:

    
def factory(aClass,*args):
    return aClass(*args)

class People:
    def __init__(self,name):
        self.name = name
        print(name)
a = factory(People,"aa")   #工厂式输出一个类

aa



In [ ]: