python实现
#!/usr/bin/python #coding:utf8 ‘‘‘ Singleton ‘‘‘ class Singleton(object): ‘‘‘‘‘ A python style singleton ‘‘‘ def __new__(cls, *args, **kw): if not hasattr(cls, ‘_instance‘): org = super(Singleton, cls) cls._instance = org.__new__(cls, *args, **kw) return cls._instance if __name__ == ‘__main__‘: class SingleSpam(Singleton): def __init__(self, s): self.s = s def __str__(self): return self.s s1 = SingleSpam(‘spam‘) print id(s1), s1 s2 = SingleSpam(‘spa‘) print id(s2), s2 print id(s1), s1