[Python-Dev] deprecation of abstractstaticmethod and abstractclassmethod (original) (raw)

Nathaniel Smith njs at pobox.com
Wed May 15 15:48:15 EDT 2019

I don't care about the deprecation either way. But can we fix the individual decorators so both orders work? Even if it requires a special case in the code, it seems worthwhile to remove a subtle user-visible footgun.

On Wed, May 15, 2019, 12:39 Ethan Furman <ethan at stoneleaf.us> wrote:

In issue 11610* abstractclassmethod and abstractstaticmethod were deprecated, apparently because they were redundant with the new technique of calling classmethod or staticmethod followed by a call to abstractmethod. To put it in code:

# deprecated class Foo(ABC): @abstractclassmethod def foohappens(cls): # do some fooey stuff # the new(er) way class Foo(ABC): @classmethod @abstractmethod def foohappens(cls): # do some fooey stuff

I would like to remove the deprecated status of abstractclassmethod and abstractstaticmethod mainly because: - using the combined decorator is easy to get right (@abstractmethod followed by @classmethod doesn't work) - getting the order wrong can be hard to spot and fix Obviously, decorator order matters for many, if not most, decorators out there -- so why should these two be any different? Because 'abstract', 'class', and 'static' are adjectives -- they're describing the method, rather than changing it**; to use an example, what is the difference between "hot, dry sand" and "dry, hot sand"? The sand is just as dry and just as hot either way. In a debugging session looking at: @abstractmethod @classmethod def somefunc(self, this, that, theother): # many # many ... ... ... # many # lines # of # code Not noticing that the two decorators are in reverse order would be very easy to do. Because order matters here, but cognitively should not, a helper function to make sure it is always done right is a prime candidate to be added to a module -- and, luckily for us, those helper functions already exist! Unfortunately, they are also deprecated, discouraging their use, when we should be encouraging their use. What are the reasons to /not/ remove the deprecation? -- Ethan

* https://bugs.python.org/issue11610 ** I realize that abstractmethod does actually change the function, but that's an implementation detail.

Python-Dev mailing list Python-Dev at python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/njs%40pobox.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20190515/8a048814/attachment-0001.html>

More information about the Python-Dev mailing list