Python单例模式的两种实现方法

import threading 
 
class Singleton(object): 
  __instance = None 
 
  __lock = threading.Lock()  # used to synchronize code 
 
  def __init__(self): 
    "disable the __init__ method" 
 
  @staticmethod 
  def getInstance(): 
    if not Singleton.__instance: 
      Singleton.__lock.acquire() 
      if not Singleton.__instance: 
        Singleton.__instance = object.__new__(Singleton) 
        object.__init__(Singleton.__instance) 
      Singleton.__lock.release() 
    return Singleton.__instance 

#encoding=utf-8 
def singleton(cls): 
  instances = {} 
  def getInstance(): 
    if cls not in instances: 
      instances[cls] = cls() 
    return instances[cls] 
  return getInstance 
 
@singleton 
class SingletonClass: 
  pass 
 
if __name__ == '__main__': 
  s = SingletonClass() 
  s2 = SingletonClass() 
  print s 
  print s2 
 

import threading 
 
class Sing(object): 
  def __init__(): 
    "disable the __init__ method" 
 
  __inst = None # make it so-called private 
 
  __lock = threading.Lock() # used to synchronize code 
 
  @staticmethod 
  def getInst(): 
    Sing.__lock.acquire() 
    if not Sing.__inst: 
      Sing.__inst = object.__new__(Sing) 
      object.__init__(Sing.__inst) 
    Sing.__lock.release() 
    return Sing.__inst