【Python进阶】单例模式

记录测试点滴2024-06-29 8:12

1.单例模式

作用：保证某一类只有一个实例存在

2.实现单例模式的方式

模块导入
*

  文件1.py

      class Test:

          def __init__(self,name):


              self.name = name



      obj = Test("何必")


  文件2.py

    from 文件1.py import obj  # 仅有一个实例对象

类装饰器
*

  def singleton_model(func):

      obj = None

      def wrapper(*args,**kwargs):

          nonlocal obj

          if not obj:

               obj = func(*args,**kwargs)

          return obj
      return wrapper


  @singleton_model  # Test = singleton_model(Test)
  class Test:
       def __init__(self,name):

          self.name = name

  obj = Test("何必")

  obj2 = Test("呵呵") #得到的对象内存地址跟obj一致

类绑定方法
*

  class Test:

      obj = None

      def __init__(self,name):

          self.name = name


      @classmethod

      def get_obj(cls,*args,**kwargs):  # 在类方法内部处理

          if not cls.obj:

              cls.obj = cls(*args,**kwargs)

          return cls.obj


  obj = Test.get_obj("何必")

__new__方法
*

  class Test:

      obj = None

      def __init__(self,name):

          self.name = name


      def __new__(cls,*args,**kwargs):

          if not cls.obj:

              cls.obj = super().__new__(cls)

          return cls.obj


  obj = Test("何必")

  obj2 = Test("呵呵")

元类
*

  class MyType(type):

      obj = None

      def __call__(self,*args,**kwargs):

          if not self.obj:
              
              self.obj = self.__new__(self)

          self.__init__(self.obj,*args,**kwargs)
              
          return self.obj    


  class Test(metaclass=MyType):


      def __init__(self,name):

          self.name = name


     


  obj = Test("何必")

  obj2 = Test("呵呵")

并发