[Python-Dev] PEP: Adding data-type objects to Python

["Martin v. Löwis"]

Travis E. Oliphant schrieb:
>> As I unification mechanism, I think it is insufficient. I doubt it
>> can express all the concepts that ctypes supports.
>>
> 
> Please clarify what you mean.
> 
> Are you saying that a single object can't carry all the information 
> about binary data that ctypes allows with it's multi-object approach?

I'm not sure what you mean by "single object". If I use the tuple
syntax, e.g.

datatype((float, (3,2))

There are also multiple objects (the float, the 3, and the 2). You
get a single "root" object back, but so do you in ctypes.

But this isn't really what I meant. Instead, I think the PEP lacks
various concepts from C data types, such as pointers, unions,
function pointers, alignment/packing.

> In the mean-time, how are other packages supposed to communicate binary 
> information about data with each other?

This is my other question. Why should they?

> Remember the context that the data-format object is presented in.  Two 
> packages need to share a chunk of memory (the package authors do not 
> know each other and only have and Python as a common reference).  They 
> both want to describe that the memory they are sharing has some 
> underlying binary structure.

Can you please give an example of such two packages, and an application
that needs them share data?

Regards,
Martin