[Python-Dev] idea for data-type (data-format) PEP (original) (raw)

Alexander Belopolsky alexander.belopolsky at gmail.com
Fri Nov 3 02:55:41 CET 2006

On Nov 2, 2006, at 8:04 PM, Greg Ewing wrote:

I think the datatype object should almost certainly be immutable. Since it's separated from the data it's describing, it's possible for one datatype object to describe multiple chunks of data. So you wouldn't want to mutate one in case it's being used for something else that you don't know about.

I only mentioned that the datatype object would be mutable at C level
because changing the object instead of deleting and creating a new
one could be a valid optimization in situations where the object is
know not to be shared.

My main concern was that in ctypes the size of an array is a part of
the datatype object and this seems to be redundant if used for the
buffer protocol. Buffer protocol already reports the size of the
buffer as a return value of bf_get*buffer methods.

In another post, Greg Ewing wrote:

numpy.array(array.array('d',[1,2,3]))

and leave-out the buffer object all together.

I think the buffer object in his example was just a placeholder for "some arbitrary object that supports the buffer interface", not necessarily another NumPy array.

Yes, thanks. In fact numpy.array(array.array('d',[1,2,3])) already
works in numpy (I think because numpy knows about the standard
library array type). In my example, I wanted to use an object that
supports buffer protocol and little else.

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