[Python-Dev] Why does _pyio.*.readinto have to work with 'b' arrays?

[Nick Coghlan]

On 15 June 2014 14:57, Nikolaus Rath <Nikolaus at rath.org> wrote:
> On 06/14/2014 09:31 PM, Nick Coghlan wrote:
>> On 15 June 2014 10:41, Benjamin Peterson <benjamin at python.org> wrote:
>>> On Sat, Jun 14, 2014, at 15:39, Nikolaus Rath wrote:
>>>> It seems to me that a much cleaner solution would be to simply declare
>>>> _pyio's readinto to only work with bytearrays, and to explicitly raise a
>>>> (more helpful) TypeError if anything else is passed in.
>>>
>>> That seems reasonable. I don't think _pyio's behavior is terribly
>>> important compared to the C _io module.
>>
>> _pyio was written before the various memoryview fixes that were
>> implemented in Python 3.3 - it seems to me it would make more sense to
>> use memoryview to correctly handle arbitrary buffer exporters (we
>> implemented similar fixes for the base64 module in 3.4).
>
> Definitely. But is there a way to do that without writing C code?

Yes, Python level reshaping and typecasting of memory views is one of
the key enhancements Stefan implemented for 3.3.

>>> from array import array
>>> a = array('b', b'x'*10)
>>> am = memoryview(a)
>>> a
array('b', [120, 120, 120, 120, 120, 120, 120, 120, 120, 120])
>>> am[:3] = memoryview(b'foo').cast('b')
>>> a
array('b', [102, 111, 111, 120, 120, 120, 120, 120, 120, 120])

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia