UserList - which methods needs to be overriden?

[Michael Selik]

On Fri, Jun 10, 2016 at 9:18 AM Michael Selik <michael.selik at gmail.com>
wrote:

>
>
> On Fri, Jun 10, 2016, 4:05 AM Nagy László Zsolt <gandalf at 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 at 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.
>>
>> 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.
>>
>
If you find that extend is indeed a bottleneck, there's an easy fix.

class NoisyList(MutableSequence):
    @noisy('extend')
    def extend(self, iterable):
        self.container.extend(iterable)