a.实例化类
实例化一个类时
1. 创建一个对象,调用__new__方法,如果没有会调用父类的__new__方法
2. 调用__init__方法
3. 返回对象的引用
class Dog(object):
def __init__(self):
print("---init方法---") def __new__(cls, *args, **kwargs):
print("---new方法---") xtq = Dog() #---------结果--------- ---new方法---
b. 单例
class Dog(object):
_instance = None
_init_flag = False
def __new__(cls, *args , **kwargs): #cls指向Dog
if cls._instance == None:
cls._instance = object.__new__(cls)
return cls._instance
else:
return cls._instance
def __init__(self,name):
if Dog._init_flag == False:
self.name = name
Dog._init_flag = True
a = Dog("旺财")
print(a.name)
b = Dog("啸天犬")
print(b.name)
#----------------结果-----------------
旺财
旺财