On Fri, Jun 10, 2016, 4:05 AM Nagy László Zsolt <gand...@shopzeus.com> wrote:
> 2016.06.10. 0:38 keltezéssel, Michael Selik írta: > > On Thu, Jun 9, 2016 at 5:07 AM Nagy László Zsolt <gand...@shopzeus.com> > wrote: > >> I would like to create a collections.UserList subclass that can notify >> others when the list is mutated. >> > > Why not subclass MutableSequence instead? The ABC will tell you which > methods to override (the abstract ones). The mixin methods rely on those > overrides. > > I'm not sure wich one is the best. Peter wrote that UserList was left in > collections only for backward compatiblity. This might be a point against > using UserList. The thing with MutableSequence is that it is quite > inefficient. For example, it implements clear() by calling pop() in a loop. > It implements extend() by calling append() in a loop. And we all know that > the built-in extend() method of the list object is much more efficient. It > is true that by overriding the abstract methods, I'll get a functional list > like object, but we all know that > > There should be one-- and preferably only one --obvious way to do it. > > > Which one is that? :-) > The easiest, most beautiful way that is sufficiently fast. Use MutableSequence until you discover that extend is actually the bottleneck in your program. > -- https://mail.python.org/mailman/listinfo/python-list
