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

[Serhiy Storchaka]

On 12.10.16 08:03, Nathaniel Smith wrote:
> On Tue, Oct 11, 2016 at 9:08 PM, INADA Naoki <songofacandy at gmail.com> wrote:
>> From Python 3.4, bytearray is good solution for I/O buffer, thanks to
>> #19087 [1].
>> Actually, asyncio uses bytearray as I/O buffer often.
>
> Whoa what?! This is awesome, I had no idea that bytearray had O(1)
> deletes at the front. I literally reimplemented this myself on type of
> bytearray for some 3.5-only code recently because I assumed bytearray
> had the same asymptotics as list, and AFAICT this is totally
> undocumented. Shouldn't we write this down somewhere? Maybe here? ->
> https://docs.python.org/3/library/functions.html#bytearray

I afraid this is CPython implementation detail (like string 
concatenation optimization). Other implementations can have O(N) deletes 
at the front of bytearray.