单例实现/pickle序列化模块

目录

• 单例模式实现的多种方式
• pickle序列化模块

单例模式实现的多种方式

方式一

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

obj = C1.singleton()
obj2 = C1.singleton()
obj3 = C1.singleton()
print(id(obj),id(obj2),id(obj3))
obj4 = C1('kevin',28)
obj5 = C1('tony', 38)
print(id(obj4))
print(id(obj5))

方式二

class Mymeta(type):
    def __init__(self, name, bases, dict):  # 定义类Myslq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, dict)

    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))

方式三

'''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')

方式四

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(id(obj1))
print(id(obj2))
print(id(obj3))

obj4 = Mysql('1.1.1.3',3307)
obj5 = Mysql('1.1.1.4',3308)
print(id(obj4))
print(id(obj5))

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
    
 
"""
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 C1:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def func1(self):
        print('from func1')

    def func2(self):
        print('from func2')

obj = C1('jason', 18)

# import json
# with open(r'a.txt','w',encoding='utf8') as f:
#     json.dump(obj,f)
import pickle
with open(r'a.txt','wb') as f:
    pickle.dump(obj,f)
with open(r'a.txt','rb') as f:
    data = pickle.load(f)
print(data)
data.func1()
data.func2()
print(data.name)