Python单例模式研究

方法一

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

 1.禁用__init__方法，不能直接创建对象。

 2.__instance，单例对象私有化。

 3.@staticmethod，静态方法，通过类名直接调用。

 4.__lock，代码锁。

 5.继承object类，通过调用object的__new__方法创建单例对象，然后调用object的__init__方法完整初始化。

 6.双重检查加锁，既可实现线程安全，又使性能不受很大影响。

方法二：使用decorator

#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

也应该加上线程安全

附：性能没有方法一高

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