On Thu, Dec 5, 2013 at 2:22 PM, Ethan Furman <et...@stoneleaf.us> wrote:
> On 12/05/2013 10:56 AM, Alexander Belopolsky wrote: > >> On Thu, Dec 5, 2013 at 1:24 PM, Guido van Rossum wrote: >> >>> >>> How would you get the docstrings in? [...] >>> >> >> One way to reduce the amount of boilerplate code is to make abstractmethod >> to supply raise NotImplementedError body when none is given. Then you can >> write >> >> class Foo: >> @abc.abstractmethod >> def do_bar(self): >> """perform bar""" >> >> The docstring will be required when skipping the body which is probably a >> good thing. >> > > How will abstractmethod know its function has no body? > Technically you could inspect the code object of the method. to figure out if the body is empty. But I would be very leery of this being a default behaviour. Raising NotImplementedError is not necessarily what the default result should be for a method. If you are building a class that supports multiple inheritance you will be calling super().do_bar() almost blindly which, if you are not careful, will raise NotImplementedError and that might not be appropriate. Maybe returning None is more reasonable, maybe raising TypeError. But support a default blindly like this can promote bad practices. You can see all of changes I had to make for importlib.abc in Python 3.4 to have API-matching default exceptions and return values instead of blindly raising NotImplementedError as a lesson learned: http://docs.python.org/3.4/library/importlib.html#module-importlib.abc. Hunt down Thomas Wouters at PyCon if you want to hear the same arguments he gave me as to why blindly raise NotImplementedError is bad.
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