bound method/unbound method/function

class _C:
    def _m(self): pass

c = _C()
c._m
>    
_C._m

_C.__dict__['_m']

==========================================
type(_C.__dict__['_m'])

type(_C._m)

type(c._m)

==========================================
func

func.im_func

func.im_self is None
True # 因为这是一个unbound method
func.im_class

实际上类的方法都会被转换为非数据型描述符

def demo_function(*args,**kwargs):
    print args,kwargs

class FooClass(object):
    def demo_method(self):
        pass

    demo_method2 = demo_function

foo_instance = FooClass()

print FooClass.__dict__['demo_method2']() #什么输出都没有
print FooClass.demo_method2() # 报错TypeError: unbound method demo_function() must be called with FooClass instance as first argument (got nothing instead)也就是说，python回去检查第一个参数是什么
print FooClass.demo_method2(foo_instance )
print foo_instance.demo_method2()