python基类如何判断子类是否覆盖了它的方法？

Question

这是我的猜测,这不起作用:

class BaseClass(object):
    def foo(self):
        return 'foo'
    def bar(self):
        return 'bar'
    def methods_implemented(self):
        """This doesn't work..."""
        overriden = []
        for method in ('foo', 'bar'):
            this_method = getattr(self, method)
            base_method = getattr(BaseClass, method)
            if this_method is not base_method:
                overriden.append(method)
        return overriden

class SubClass(BaseClass):
    def foo(self):
        return 'override foo'

o = SubClass()
o.methods_implemented()

理想情况下,methods_implemented()将返回['foo'].

怎么样？

(为什么我要这样做？我的基类是一个HTTP资源类,它有方法GET,POST等.默认情况下它们返回405方法未实现.它还有一个方法OPTIONS,它应返回200响应,标题为Allow设置为任何子类实现的方法.)

Answer 1

也许这个？

>>> class BaseClass(object):
...     def foo(self):
...         return 'foo'
...     def bar(self):
...         return 'bar'
...     def methods_implemented(self):
...         """This does work."""
...         overriden = []
...         for method in ('foo', 'bar'):
...             this_method = getattr(self, method)
...             base_method = getattr(BaseClass, method)
...             if this_method.__func__ is not base_method.__func__:
...                 overriden.append(method)
...         return overriden
... 
>>> class SubClass(BaseClass):
...     def foo(self):
...         return 'override foo'
... 
>>> o = SubClass()
>>> o.methods_implemented()
['foo']

这将检查绑定方法后面的函数对象是否相同.

请注意,在Python 2.6之前,该__func__属性已命名im_func.