zoukankan      html  css  js  c++  java
  • 单例模式

    单例模式:

    多次实例化的结果指向同一个实例

    settings文件内容:
    IP='1.1.1.1'
    PORT=3306
    ================================================================
    单例模式实现方式一:
    import settings

    class MySQL:
    __instance=None
    def __init__(self, ip, port):
    self.ip = ip
    self.port = port

    @classmethod
    def from_conf(cls):
    if cls.__instance is None:
    cls.__instance=cls(settings.IP, settings.PORT)
    return cls.__instance
    obj1=MySQL.from_conf()
    obj2=MySQL.from_conf()
    obj3=MySQL.from_conf()
    obj4=MySQL('1.1.1.3',3302)
    print(obj1)
    print(obj2)
    print(obj3)
    print(obj4)
    ==========================================================================
    单例模式实现方式二:
    import settings

    def singleton(cls):
    _instance=cls(settings.IP,settings.PORT)
    def wrapper(*args,**kwargs):
    if len(args) !=0 or len(kwargs) !=0:
    obj=cls(*args,**kwargs)
    return obj
    return _instance
    return wrapper

    @singleton #MySQL=singleton(MySQL) #MySQL=wrapper
    class MySQL:
    def __init__(self, ip, port):
    self.ip = ip
    self.port = port

    obj1=MySQL() #wrapper()
    obj2=MySQL() #wrapper()
    obj3=MySQL() #wrapper()
    obj4=MySQL('1.1.1.3',3302) #wrapper('1.1.1.3',3302)
    print(obj1)
    print(obj2)
    print(obj3)
    print(obj4)

    ==========================================================================

     

    单例模式实现方式三:
    import settings

    class Mymeta(type):
    def __init__(self,class_name,class_bases,class_dic):
    #self=MySQL这个类
    self.__instance=self(settings.IP,settings.PORT)

    def __call__(self, *args, **kwargs):
    # self=MySQL这个类
    if len(args) != 0 or len(kwargs) != 0:
    obj=self.__new__(self)
    self.__init__(obj,*args, **kwargs)
    return obj
    else:
    return self.__instance

    class MySQL(metaclass=Mymeta): #MySQL=Mymeta(...)
    def __init__(self, ip, port):
    self.ip = ip
    self.port = port


    obj1=MySQL()
    obj2=MySQL()
    obj3=MySQL()
    obj4=MySQL('1.1.1.3',3302)
    print(obj1)
    print(obj2)
    print(obj3)
    print(obj4)

    ==========================================================================

     

    单例模式实现方式四:
    def f1():
    from singleton import instance
    print(instance)

    def f2():
    from singleton import instance,My
    SQL
    print(instance)
    obj=MySQL('1.1.1.3',3302)
    print(obj)

    f1()
    f2()

    singletod文件内容:
    import settings

    class MySQL:
    print('run....')
    def __init__(self, ip, port):
    self.ip = ip
    self.port = port

    instance=MySQL(settings.IP,settings.PORT)
  • 相关阅读:
    小白初学iOS中OTA部署(适应iOS7.1)
    CocoaPods管理本地库简单步骤
    CocoaPods问题记录
    UIPanGestureRecognizer下方法
    2013年度总结(反思篇)
    iOS7中cell的分割线右移的解决方法
    接触CocoaPods遇到的问题
    iOS摄像头问题
    iPhone4激活出错,菜鸟试验!!!!!
    详解UIPickerView
  • 原文地址:https://www.cnblogs.com/zhangpang/p/9580411.html
Copyright © 2011-2022 走看看