[Numpy-discussion] Add guaranteed no-copy to array creation and reshape?

[Ralf Gommers]

On Thu, Jan 10, 2019 at 11:21 AM Feng Yu <rainwoodman at gmail.com> wrote:

> Hi Todd,
>
> I agree a flag is more suitable than classes.
>
> I would add another bonus of a flag than a function argument is to avoid
> massive contamination of function signatures for a global variation of
> behavior that affects many functions.
>

I like this suggestion. Copy behavior fits very nicely with existing flags
(e.g. UPDATEIFCOPY, WRITEABLE) and avoids both namespace pollution and
complication docstrings.

Ralf


> Yu
>
> On Wed, Jan 9, 2019 at 11:34 PM Todd <toddrjen at gmail.com> wrote:
>
>> On Mon, Jan 7, 2019, 14:22 Feng Yu <rainwoodman at gmail.com wrote:
>>
>>> Hi,
>>>
>>> Was it ever brought up the possibility of a new array class (ndrefonly,
>>> ndview) that is strictly no copy?
>>>
>>> All operations on ndrefonly will return ndrefonly and if the operation
>>> cannot be completed without making a copy, it shall throw an error.
>>>
>>> On the implementation there are two choices if we use subclasses:
>>>
>>> - ndrefonly can be a subclass of ndarray. The pattern would be subclass
>>> limiting functionality of super, but ndrefonly is a ndarray.
>>> - ndarray as a subclass of ndarray. Subclass supplements functionality
>>> of super. : ndarray will not throw an error when a copy is necessary.
>>> However ndarray is not a ndarray.
>>>
>>> If we want to be wild they do not even need to be subclasses of each
>>> other, or maybe they shall both be subclasses of something more
>>> fundamental.
>>>
>>> - Yu
>>>
>>
>> I would prefer a flag for this.  Someone can make an array read-only by
>> setting `arr.flags.writable=False`.  So along those lines, we could have a
>> `arr.flags.copyable` flag that if set to `False` would result in an error
>> of any operation tried to copy the data.
>>
>>> _______________________________________________
>> NumPy-Discussion mailing list
>> NumPy-Discussion at python.org
>> https://mail.python.org/mailman/listinfo/numpy-discussion
>>
> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion at python.org
> https://mail.python.org/mailman/listinfo/numpy-discussion
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/numpy-discussion/attachments/20190110/7840b0d2/attachment.html>