On Sat, Feb 14, 2015 at 01:26:36PM -0500, Alexander Belopolsky wrote: > On Sat, Feb 14, 2015 at 7:23 AM, Steven D'Aprano <[email protected]> > wrote: > > > Why can't int, str, list, tuple etc. be more like datetime? > > > They are. In all these types, class methods call subclass constructors but > instance methods don't.
But in datetime, instance methods *do*. Sorry that my example with .today() was misleading. py> from datetime import datetime py> class MyDatetime(datetime): ... pass ... py> MyDatetime.today() MyDatetime(2015, 2, 15, 12, 45, 38, 429269) py> MyDatetime.today().replace(day=20) MyDatetime(2015, 2, 20, 12, 45, 53, 405889) > In the case of int, there is a good reason for this behavior - bool. In > python, we want True + True == 2. Sure. But bool is only one subclass. I expect that it should be bool's responsibility to override __add__ etc. to return an instance of the parent class (int) rather have nearly all subclasses have to override __add__ etc. to return instances of themselves. -- Steve _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com