Python单例模式研究
方法一Python代码
[*]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
Python代码
[*]#encoding=utf-8
[*]def singleton(cls):
[*] instances = {}
[*] def getInstance():
[*] if cls not in instances:
[*] instances = cls()
[*] return instances
[*] 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
Python代码
[*]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
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