python - 指向 Python 中静态方法的指针

Question

为什么在下面的代码中，使用类变量作为方法指针会导致未绑定(bind)方法错误，而使用普通变量却可以:

class Cmd: 
    cmd = None

    @staticmethod   
    def cmdOne():
        print 'cmd one'

    @staticmethod   
    def cmdTwo():
        print 'cmd two'

def main():
    cmd = Cmd.cmdOne
    cmd() # works fine

    Cmd.cmd = Cmd.cmdOne        
    Cmd.cmd() # unbound error !!

if __name__=="__main__":
    main()

完整错误:

TypeError: unbound method cmdOne() must be called with Cmd instance as 
           first argument (got nothing instead)

Answer 1

需要使用staticmethod()来转换函数:

Cmd.cmd = staticmethod(Cmd.cmdOne)