单列模式实现的多种方法
单列模式实现的多种方法方式
class C1:
__instance = None
def __init__(self, name, age):
self.name = name
self.age = age
@classmethod
def singleton(cls):
if not cls.__instance:
cls.__instance = cls('jason', 18)
return cls.__instance
obj1 = C1.singleton()
obj2 = C1.singleton()
obj3 = C1.singleton()
print =(id(obj1),id(obj2),id(obj3))
obj4 = C1('kevin',28)
obj5 = C1('tony',39)
print(id.(obj4),id(obj5)
class Mymeta(type):
def __init__(self, name, bases, dic): # 定义类Mysql时就触发
# 事先先从配置文件中取配置来造一个Mysql的实例出来
self.__instance = object.__new__(self) # 产生对象
self.__init__(self.__instance, 'jason', 18) # 初始化对象
# 上述两步可以合成下面一步
# self.__instance=super().__call__(*args,**kwargs)
super().__init__(name, bases, dic)
def __call__(self, *args, **kwargs): # Mysql(...)时触发
if args or kwargs: # args或kwargs内有值
obj = object.__new__(self)
self.__init__(obj, *args, **kwargs)
return obj
return self.__instance
class Mysql(metaclass=Mymeta):
def __init__(self, name, age):
self.name = name
self.age = age
obj1 = Mysql()
obj2 = Mysql()
print(id(obj1), id(obj2))
obj3 = Mysql('tony', 321)
obj4 = Mysql('kevin', 222)
print(id(obj3), id(obj4))
'''基于模块的单例模式:提前产生一个对象 之后导模块使用'''
class C1:
def __init__(self, name):
self.name = name
obj = C1('jason')
def outer(cls):
_instance = cls('jason', 18)
def inner(*args, **kwargs):
if args or kwargs:
obj = cls(*args, **kwargs)
return obj
return _instance
return inner
@outer # Mysql=outer(Mysql)
class Mysql:
def __init__(self, host, port):
self.host = host
self.port = port
obj1 = Mysql()
obj2 = Mysql()
obj3 = Mysql()
print(obj1 is obj2 is obj3) # True
obj4 = Mysql('1.1.1.3', 3307)
obj5 = Mysql('1.1.1.4', 3308)
print(obj3 is obj4) # False
pickle序列化模块
优势:能够序列化python中所有的类型
缺陷:只能够在python中使用,无法跨语言传输
需求:产生一个对象并保存到文件中,取出来还是一个对象
class Myclass:
def __init__(self, name):
self.name = name
def choice_course(self):
print(f'{self.name}正在选课')
obj = Myclass('jason')
# print(obj) # <__main__.Myclass object at 0x000001F5032B3B50>
# obj.choice_course() # jason正在选课
import pickle
"""pickle序列化把对象保存到文件中"""
with open(r'a.txt', 'wb') as f:
pickle.dump(obj, f)
"""pickle反序列化从文件中取出对象"""
with open(r'a.txt', 'rb') as f:
data = pickle.load(f)
print(data) # <__main__.Myclass object at 0x0000012502804BB0>
data.choice_course() # jason正在选课
标签:__,.__,name,单列,模块,Mysql,pickle,self,def
From: https://www.cnblogs.com/lvqingmei/p/16874674.html