python实现独身模式，python实现独身,class A:

python实现独身模式，python实现独身,class A:

class A:    # attribute known to function Singleton    _instance = None    def foo(self):        return id(self)def Singleton(klass):    if not klass._instance:        klass._instance = klass()    return klass._instance# subclass Aclass B(A):    passb = Singleton(A)c = Singleton(B)d = Singleton(A)print id(b),b.foo()print id(c),c.foo()print id(d),c.foo()

输出：

7963404 79634047963404 79634047963404 7963404