[Python-Dev] why different between staticmethod and classmethod on non-callable object? (original) (raw)

xiaobing jiang s7v7nislands at gmail.com
Wed Sep 2 10:24:30 CEST 2009

the three types: function, classmethod, staticmethod are descriptors. but staticmethod's get return the orignal value, others return object of instancemethod. (from souce in Objects/funcobject.c) so the staticmethod just like a wrap that make the wrapped object 'frozen'. like in your example. is it right? the name and document are mis-understanded.

thanks

2009/9/2 P.J. Eby <pje at telecommunity.com>:

At 08:50 PM 9/1/2009 -0400, Terry Reedy wrote:

Greg Ewing wrote:

Benjamin Peterson wrote:

It depends on whether you're keeping the "callable" object around or not. Somebody could add a call method later. Good point. Removing the check sounds like the right thing to do, then. Both classmethod & staticmethod are documented as having a function (callable, as I interprete that) as their single argument. Seems reasonable to me. Turning the argument into a function after the fact seems like a really esoteric use case. The main use case for staticmethod is to prevent get from being called on an object retrieved from a class or an instance.  It just happens that the most common types of objects you'd want to do that on are functions. However, if for some reason you intend to make a descriptor available as an attribute (via a class default), then wrapping it with staticmethod is the only easy way to do it. For example, if you're writing a class whose instances have an attribute that holds a "property" instance, and you want to provide a class-level default, the simplest way to do it is to wrap the default property instance with staticmethod, so that it's not treated as a property of the class/instance. (Property instances are of course not callable.)

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