[Python-Dev] PEP 467: Minor API improvements to bytes, bytearray, and memoryview

[Steven D'Aprano]

On Wed, Jun 08, 2016 at 02:17:12AM +0300, Paul Sokolovsky wrote:
> Hello,
> 
> On Tue, 07 Jun 2016 15:46:00 -0700
> Ethan Furman <ethan at stoneleaf.us> wrote:
> 
> > On 06/07/2016 02:33 PM, Paul Sokolovsky wrote:
> > 
> > >> This PEP proposes to deprecate that behaviour in Python 3.6, and
> > >> remove it entirely in Python 3.7.
> > >
> > > Why the desire to break applications of thousands and thousands of
> > > people? 

I'm not so sure that *thousands* of people are relying on this 
behaviour, but your point is taken that it is a backwards-incompatible 
change.


> > > Besides, bytes(3) behavior is very logical. Everyone who
> > > knows what malloc(3) does also knows what bytes(3) does.

Most Python coders are not C coders. Knowing C is not and should not be 
a pre-requisite for using Python.


> > > Who
> > > doesn't, can learn, and eventually be grateful that learning Python
> > > actually helped them to learn other language as well.

I really don't think that learning Python will help with C.


> > Two reasons:
> > 
> > 1) bytes are immutable, so creating a 3-byte 0x00 string seems
> >     ridiculous;
> 
> There's nothing ridiculous in sending N zero bytes over network,
> writing to a file, transferring to a hardware device.

True, but there is a good way of writing N identical bytes, not limited 
to nulls, using the replication operator:

py> b'\xff'*10
b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff'

which is more useful than `bytes(10)` since that can only produce 
zeroes.


> That however
> raises questions e.g. how to (efficiently) fill a (subsection) of
> bytearray with something but a 0

Slicing.

py> b = bytearray(10)
py> b[4:4] = b'\xff'*4
py> b
bytearray(b'\x00\x00\x00\x00\xff\xff\xff\xff\x00\x00\x00\x00\x00\x00')


-- 
Steve