Python中的单例模式

单例模式的三个要点

• 单例类只能创建一个实例
• 单例类自己创建自己唯一的实例
• 单例类给其他所有对象提供实例

单例模式的实现

• 导入模块

• 使用装饰器

  from functools import wraps
  def singleton(cls):
      instance = {}
      @wraps(cls)
      def wrapper(*args,**kwargs):
          if cls not in instance:
              instance[cls] = cls(*args,**kwargs)
          return instance[cls]
      return wrapper
  @singleton
  class Test(object):
      def __init__(self,x):
          self.x = x
  test1 = Test(1)
  test2 = Test(2)
  

• 使用类

  class Singleton(object):
      def __init__(self,x):
          self.x = x
      @classmethod
      def instance(cls,*args,**kwargs):
          if not hasattr(Singleton,'instance'):
              Singleton.instance = Singleton(*args,**kwargs)
          return Singleton.instance
  test = Singleton() 
  

• 使用_ _ new_ _

  import threading
  import time
  class Singleton(object):
      insatnce = None
      lock = threading.Rlock()
      def __init__(self,name):
          self.name = name
      def __new__(cls,*args,**kwargs):
          with cls.lock:
              if not cls.instance:
                  cls.instance = object.__new__(cls)
          return cls.instance
  def func():
      obj = Singleton("zevin")
      print(obj)
  for i in range(10):
      t= threading.Thread(target=func)
      t.start()