class C:def func(self):pass
class A(C):def func1(self):print(444)
class B(A):def func2(self):print(66)print(issubclass(B,C))  B与C是继承关系
print(isinstance(B,C))  B与C是继承关系不是父类与子类关系
#####
True
Flse

class A:b = '666'def func(self):print(333)
a = A()
print(getattr(A,'b'))   类反射
c = getattr(a,'func')   对象反射
d = c()
####
666
333

 import  osgetattr(os,'rename')('hehe','fuck')

import sys
def login():print('登陆成功')
def register():print('注册成功')
func = input('请输入')
if hasattr(sys.modules['__main__'],func):getattr(sys.modules['__main__'],func)()

class A:    bb = 'haha'    def __init__(self,name):        self.name = name

    def wahaha(self):        print('wahahahahaha')

def qqxing(self):    print('qqqqqxing')

a = A('alex')setattr(A,'qqxing',qqxing)           为类在增加动态属性# setattr(a,'qqxing',qqxing)          为对象增加属性print(A.__dict__)print(a.__dict__)a.qqxing()                        delattr(A,'bb')                     删除类的静态属性delattr(A,'qqxing')                  删除类的动态属性print(A.__dict__)a.qqing(a)                          为对象增加的方法的调用方式，要传参

class Teacher:def __init__(self,name,age):self.name = nameself.age = agedef __str__(self):return "Teacher's object %s"%self.namedef __repr__(self):return 'repr function %s'%self.name
a = Teacher('alex',80)
b = Teacher('egon',80)
print(str(a))
print(repr(a))
print(a)
print(b)
#####
Teacher's object alex
repr function alex
Teacher's object alex
Teacher's object egon可以看到  当__str__ 和 __repr__同时存在时  print默认去找str方法

class Teacher:def __init__(self,name,age):self.name = nameself.age = age# def __str__(self):#     return "Teacher's object %s"%self.namedef __repr__(self):return 'repr function %s'%self.name
a = Teacher('alex',80)
b = Teacher('egon',80)
print(str(a))
print(repr(a))
print(a)
print(b)
当我们把str方法注释掉的时候 print自动去找了repr的方法  而print(str())也去找了repr的方法

class Teacher:def __init__(self,name,age):self.name = nameself.age = agedef __str__(self):return "Teacher's object %s"%self.name# def __repr__(self):#     return 'repr function %s'%self.name
a = Teacher('alex',80)
b = Teacher('egon',80)
print(str(a))
print(repr(a))
print(a)
print(b)
#####
acher's object alex
<__main__.Teacher object at 0x000002201ED825F8>
Teacher's object alex
Teacher's object egon

把repr的方法注释掉的时候，print都去找了str的方法，而print(repr())的方法直接去找了父类object的repr的方法打印了内存地址
我们的出来结论：  

class B:__instance = None                        #定义一个实例def __new__(cls, *args, **kwargs):if cls.__instance is None:obj = object.__new__(cls)     创建了一个新的空间赋给了__instance  这时候__instance不再是None  cls.__instance = objreturn cls.__instancedef __init__(self,name,age):self.name = nameself.age = agedef func(self):print(self.name)
a = B('alex',80)
b = B('egon',20)
print(a)
print(b)
print(a.name)
print(b.name)
####
egon
egon这段代码中  后面实例化都是在一个内存空间中进行所以 后面每次实例化新对象都是在一个内存空间  新的把旧的覆盖

class Foo:def __init__(self,name):self.name=namedef __getitem__(self,item):return  self.__dict__[item]def __setitem__(self, key, value):self.__dict__[key]=valuedef __delitem__(self, key):print('del obj[key]时,我执行')self.__dict__.pop(key)
a = Foo('aa')
print(a['name'])
a.age = 18
a['age'] = 22
a.age = 23
del a['age']
print(a.age)
f = Foo('alex')
# f.name = ...
print(f['name'])    # f.__getitem__('name')
f['age']  = 18      # 赋值
print(f.age)         # 自带的语法
print(f['age'])     # 修改
f['age']  = 80
print(f['age'])     # 通过实现__getitem__得到的
del f['age']
print(f.age)         # 删除