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

Steven D'Aprano steve at pearwood.info
Tue Jun 7 23:09:15 EDT 2016

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

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