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Re: UserList - which methods needs to be overriden?

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  Re: UserList - which methods needs to be overriden? Michael Selik <michael.selik@gmail.com> - 2016-06-10 13:18 +0000

#109785 — Re: UserList - which methods needs to be overriden?

On Fri, Jun 10, 2016, 4:05 AM Nagy László Zsolt <gandalf@shopzeus.com>
wrote:

> 2016.06.10. 0:38 keltezéssel, Michael Selik írta:
>
> On Thu, Jun 9, 2016 at 5:07 AM Nagy László Zsolt <gandalf@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.

>

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