Re: extending PersistentList

Hello,

I have made an alternative PersistenList, but would like to know if this 
could cause me trouble later on. 

class PersistenList2(MutableSequence, Persistent):

    def __init__(self, items, owner=None):
        self.items = list(items)

    def __len__(self):
        return len(self.items)

    def __getitem__(self, index):
        return self.items[index]

    def __setitem__(self, index, value):
        self.items[index] = value
        self._p_changed = True

    def __delitem__(self, index):
        del self.items[index]
        self._p_changed = True

    def insert(self, index, value):
        self.items.insert(index, value)
        self._p_changed = True

    def __eq__(self, other):
        if isinstance(other, PersisitenList2):
            return self.items == other.items
        return self.items == other

    def __ne__(self, other):
        return not (self == other)

I have stripped out the code needed for my own project (the __dirty__ lines below, ehm). My main question is whether this will persist correctly and if there are any disadvantages compared to the standard PersistentList.


Cheers, Lars





On Friday, May 6, 2016 at 10:21:09 PM UTC+2, Lars van Gemerden wrote:
>
> Hi,
>
> I have been looking for a way to extend PersistentList in an elegant way. 
> I tried overriding the abstract methods in MutableSequence but ofcourds 
> that does not work, because UserList overrides all methods in 
> MutableSequence (don't know why; speed reasons?).
>
> I also tried this:
>
> class ServerFieldList(PersistentList):
>
>     def __init__(self, items, owner=None):
>         super(ServerFieldList, self).__init__(items)
>         self.owner = owner
>
>     def _get_changed(self):
>         return Persistent._get_changed(self)
>
>     def _set_changed(self, value):
>         Persistent._set_changed(self, value)
>         self.owner.__dirty__ = True
>
>     def _del_changed(self):
>         Persistent._del_changed(self)
>         self.owner.__dirty__ = True
>
>     _p_changed = property(_get_changed, _set_changed, _del_changed)
>
>
>
> but directly both calling the _get_changed etc methods in Persistent or using super(ServerFieldList, self) gives me an AttributeError, while i can clearly see these methods in Persistent. must have something to do with the @implementer decorator.
>
>
> Is there anyway to access the _get_changed directly, or any way to get this to work, preferably without extending all methods in PersistentList or UserList?
>
>
> Cheers, Lars  
>
>

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