On 15-02-13, Guido van Rossum wrote: > Are you willing to wait 10 days for an answer? I'm out of round tuits for > a while.
IIUC, the argument is that the Liskov Substitution Principle is a statement about how objects of a subtype behave relative to objects of a supertype, and it doesn't apply to constructors because they aren't behaviors of existing objects. So other overriding methods *should* be able to handle the same inputs that the respective overridden methods do, but constructors don't need to. Even though __init__ is written as an instance method, it seems like it's "morally" a part of the class method __new__ that's only split off for convenience. If this message is unclear, it's because I don't really understand this myself and I'm trying to articulate my best understanding of what's been said on this thread and those it links to. ijs > On Fri, Feb 13, 2015 at 10:22 AM, Alexander Belopolsky > <alexander.belopol...@gmail.com(javascript:main.compose()> wrote: > > > > > On Fri, Feb 13, 2015 at 1:19 PM, Alexander Belopolsky > > <alexander.belopol...@gmail.com(javascript:main.compose()> wrote: > > >> > > >> FWIW you're wrong when you claim that "a constructor is no different > > >> from any other method". Someone else should probably explain this > > >> (it's an old argument that's been thoroughly settled). > > > > > > > > > Well, the best answer I've got in the past [1] was "ask on python-dev > > > since Guido called the operator overriding expectation." :-) > > > > > > And let me repost this bit of history [1]: > > > > Here is the annotated pre-r82065 code: > > > > 39876 gvanrossum def __add__(self, other): > > 39876 gvanrossum if isinstance(other, timedelta): > > 39928 gvanrossum return self.__class__(self.__days + other.__days, > > 39876 gvanrossum self.__seconds + other.__seconds, > > 39876 gvanrossum self.__microseconds + other.__microseconds) > > 40207 tim_one return NotImplemented > > 39876 gvanrossum > > > > > > > > [1] http://bugs.python.org/issue2267#msg125979 > > > > > > > > > -- > --Guido van Rossum (python.org/~guido(http://python.org/~guido)) _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
