On Apr 10, 2020, at 15:53, Steele Farnsworth wrote:
>
> I have implemented a class in the C code of the collections module which has
> similar behavior to the defaultdict class. This class, dynamicdict, supplies
> values for keys that have not yet been added using a default factory
> callable,
I have often wanted this! I use defaultdict only occasionally, and every
time I do, I start out thinking it behaves the way you describe
dynamicdict. Then I read the docs again and decide I didn't actually want
defaultdict to start with, and roll something different.
On Fri, Apr 10, 2020, 6:50 PM
On Fri, Apr 10, 2020 at 06:02:25PM -0700, Andrew Barnert via Python-ideas wrote:
> (Keep in mind that defaultdict
> was added somewhere around 2.4 or 2.5, while __missing__ has only been
> there since somewhere around 2.7/3.3. I’ll bet it would be different
> if it were invented today.)
Both
I have built this data structure countless times. So I am in favor.
> Why can’t you just subclass dict and override that?
Because TypeError: multiple bases have instance lay-out conflict is one of
my least favorite errors.
Perhaps `__missing__` could be a first class part of the getitem of
proto
> On Apr 13, 2020, at 18:44, Caleb Donovick wrote:
>
> I have built this data structure countless times. So I am in favor.
Maybe you can give a concrete example of what you need it for, then? I think
that would really help the proposal. Especially if your example needs a
per-instance rather t
I've implemented the class as a stand-alone module here:
https://github.com/swfarnsworth/dynamicdict
It could in theory be made significantly more concise if `defdict_type`
were the base for this class instead of `PyDict_Type`.
On Tue, Apr 14, 2020 at 1:32 PM Andrew Barnert via Python-ideas <
p
> Besides performance, I don’t think it fits with Guido’s conception of the
protocols as being more minimal than the builtin types—e.g., set has not
just a & operator, but also an intersection method that takes 0 or more
arbitrary iterables; the set protocol has no such method, so
collections.abc.S
>> On Apr 15, 2020, at 14:08, Caleb Donovick wrote:
>>
>> Besides performance, I don’t think it fits with Guido’s conception of the
>> protocols as being more minimal than the builtin types—e.g., set has not
>> just a & operator, but also an intersection method that takes 0 or more
>> arbitrar
On Mon, Apr 13, 2020 at 06:43:53PM -0700, Caleb Donovick wrote:
> > Why can’t you just subclass dict and override that?
>
> Because TypeError: multiple bases have instance lay-out conflict is one of
> my least favorite errors.
For the benefit of the people on this list who aren't as familiar wit
> construction calls __init__ if __new__ returns an instance
Actually type's __call__ method does that, although that doesn't help my
point at all...
Your point about there being no method to perform the dispatch is good. To
get what I want without interpreter changes there would need to be som
On Apr 16, 2020, at 11:03, Caleb Donovick wrote:
>
> Or alternatively MissingMapping (or some other mixin) could define
> __getitem__ and require __getitem_impl__ and __missing__. As this wouldn't
> require any changes to anything I think it might be the best solution I have
> proposed.
I t
On Apr 16, 2020, at 12:26, Andrew Barnert wrote:
>
> Somewhere I have some code for a set of class decorators that help
> implementing mappings and sequences: you provide basic __fooitem__ methods,
> and it wraps them with methods that do all the extra stuff dict, tuple, and
> list do. IIRC, t
So, going back to the original post, dynamicdict is definitely something
I've reimplemented myself multiple times essentially exactly as your
pseudo-code in your C-command describes, just with the factory being
required to be not None (because I explicitly didn't want it to accept the
'no-factory'
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