[Python-ideas] Add recordlcass to collections module

[Wes Turner]

On Sunday, September 2, 2018, Zaur Shibzukhov <szport at gmail.com> wrote:

>
>
> ---
> *Zaur Shibzukhov*
>
>
> 2018-09-02 22:11 GMT+03:00 Wes Turner <wes.turner at gmail.com>:
>
>> Does the value of __hash__ change when attributes of a recordclass change?
>>
>
> Currently recordclass's __hash__ didn't implemented.
>

https://docs.python.org/3/glossary.html#term-hashable

https://docs.python.org/3/reference/datamodel.html#object.__hash__

http://www.attrs.org/en/stable/hashing.html


>
>> On Sunday, September 2, 2018, Zaur Shibzukhov <szport at gmail.com> wrote:
>>
>>> As the author of `recordclass` I would like to shed some light...
>>>
>>> Recorclass originated as a response to the [question](
>>> https://stackoverflow.com/questions/29290359/exis
>>> tence-of-mutable-named-tuple-in-python/29419745#29419745) on
>>> stackoverflow.
>>>
>>> `Recordclass` was conceived and implemented as a type that, by api,
>>> memory and speed, would be completely identical to` namedtuple`, except
>>> that it would support an assignment in which any element could be replaced
>>> without creating a new instance, as in ` namedtuple`. Those. would be
>>> almost identical to `namedtuple` and support the assignment (` __setitem__`
>>> / `setslice__`).
>>>
>>> The effectiveness of namedtuple is based on the effectiveness of the
>>> `tuple` type in python. In order to achieve the same efficiency it was
>>> necessary to create a type `memoryslots`. Its structure
>>> (`PyMemorySlotsObject`) is identical to the structure of` tuple`
>>> (`PyTupleObject`) and therefore takes up the same amount of memory as`
>>> tuple`.
>>>
>>> `Recordclass` is defined on top of` memoryslots` just like `namedtuple`
>>> above` tuple`. Attributes are accessed via a descriptor (`itemgetset`),
>>> which supports both` __get__` and `__set__` by the element index.
>>>
>>> The class generated by `recordclass` is:
>>>
>>> `` `
>>> from recordclass import memoryslots, itemgetset
>>>
>>> class C (memoryslots):
>>>     __slots__ = ()
>>>
>>>     _fields = ('attr_1', ..., 'attr_m')
>>>
>>>     attr_1 = itemgetset (0)
>>>     ...
>>>     attr_m = itemgetset (m-1)
>>>
>>>     def __new __ (cls, attr_1, ..., attr_m):
>>>         'Create new instance of {typename} ({arg_list})'
>>>         return memoryslots .__ new __ (cls, attr_1, ..., attr_m)
>>> `` `
>>> etc. following the `namedtuple` definition scheme.
>>>
>>> As a result, `recordclass` takes up as much memory as` namedtuple`, it
>>> supports quick access by `__getitem__` /` __setitem__` and by attribute
>>> name via the protocol of the descriptors.
>>>
>>> Regards,
>>>
>>> Zaur
>>>
>>> суббота, 1 сентября 2018 г., 10:48:07 UTC+3 пользователь Martin Bammer
>>> написал:
>>>>
>>>> Hi,
>>>>
>>>> what about adding recordclass
>>>> (https://bitbucket.org/intellimath/recordclass) to the collections
>>>> module
>>>>
>>>> It is like namedtuple, but elements are writable and it is written in C
>>>> and thus much faster.
>>>>
>>>> And for convenience it could be named as namedlist.
>>>>
>>>> Regards,
>>>>
>>>> Martin
>>>>
>>>>
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>>>>
>>>
>
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