ctypes And The WACAH Principle

[Steven D'Aprano]

On Wed, 10 Aug 2016 11:45 am, Lawrence D’Oliveiro wrote:

> GvR has said “we’re all consenting adults here”. He was referring to the
> “public/private/protected” access-control business that most
> object-oriented languages require you to go through. But there is another
> area where I think this principle applies to Python, at least in part:
> low-level access to arbitrary memory.

Well, that's certainly an idiosyncratic position to take. Most people
believe that high-level languages like Python should insulate the
programmer from low-level details, and avoid the risk of memory corruption,
buffer overflows, segmentation faults and core dumps.


[...]
> For the most part, Python doesn’t make it easy to allocate an object and
> get access to its internal memory representation. One interesting
> exception is array.array objects
> <https://docs.python.org/3/library/array.html>, which have the
> buffer_info() method, directly returning both the address and length of
> the underlying memory block. The documentation for buffer_info() says:
> 
>     When using array objects from code written in C or C++ (the only way
>     to effectively make use of this information), it makes more sense to
>     use the buffer interface supported by array objects.
> 
> Ah, I wish... I had a look at the documentation for the buffer interface
> and memory views, and found no way to make use of them from pure Python.
> Basically, the paragraph I quoted above is wrong in just about every
> important detail.

I don't understand. The documentation says that the ONLY way to use that
information is from C or C++. You have found no other way to use that
information. How is that "wrong"? How are *you* interpreting that
documentation? What are you trying (and failing) to do?

> So, for now, if I want to use Python-allocated memory with lower-level
> APIs via ctypes, the array module remains the way to go.

I really don't understand what you are trying to say. Perhaps a working code
sample might help.






-- 
Steve
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.