[Python-Dev] Adding bytes.frombuffer() constructor to PEP 467 (was: [Python-ideas] Adding bytes.frombuffer() constructor

[INADA Naoki]

On Wed, Oct 12, 2016 at 2:32 PM, Serhiy Storchaka <storchaka at gmail.com> wrote:
> On 12.10.16 07:08, INADA Naoki wrote:
>>
>> Sample code:
>>
>>     def read_line(buf: bytearray) -> bytes:
>>         try:
>>             n = buf.index(b'\r\n')
>>         except ValueError:
>>             return b''
>>
>>         line = bytes(buf)[:n]  # bytearray -> bytes -> bytes
>
>
> Wouldn't be more correct to write this as bytes(buf[:n])?

Yes, you're right!
I shouldn't copy whole data only for cast from bytearray to byte.

>
>> Adding one more constructor to bytes:
>>
>>     # when length=-1 (default), use until end of *byteslike*.
>>     bytes.frombuffer(byteslike, length=-1, offset=0)
>
>
> This interface looks unusual. Would not be better to support the interface
> of buffer in Python 2: buffer(object [, offset[, size]])?
>

It looks better.

(Actually speaking, I love deprecated old buffer for simplicity.
memoryview supports non bytes-like complex data types.)

Thanks,

-- 
INADA Naoki  <songofacandy at gmail.com>