[Python-Dev] PEP 467: Minor API improvements for bytes & bytearray

Donald Stufft donald at stufft.io
Sun Aug 17 19:16:31 CEST 2014

> On Aug 17, 2014, at 1:07 PM, Raymond Hettinger <raymond.hettinger at gmail.com> wrote:
> On Aug 17, 2014, at 1:41 AM, Nick Coghlan <ncoghlan at gmail.com <mailto:ncoghlan at gmail.com>> wrote:
>> If I see "bytearray(10)" there is nothing there that suggests "this
>> creates an array of length 10 and initialises it to zero" to me. I'd
>> be more inclined to guess it would be equivalent to "bytearray([10])".
>> "bytearray.zeros(10)", on the other hand, is relatively clear,
>> independently of user expectations.
> Zeros would have been great but that should have been done originally.
> The time to get API design right is at inception.
> Now, you're just breaking code and invalidating any published examples.
>>> Another thought is that the core devs should be very reluctant to deprecate
>>> anything we don't have to while the 2 to 3 transition is still in progress.
>>> Every new deprecation of APIs that existed in Python 2.7 just adds another
>>> obstacle to converting code.  Individually, the differences are trivial.
>>> Collectively, they present a good reason to never migrate code to Python 3.
>> This is actually one of the inconsistencies between the Python 2 and 3
>> binary APIs:
> However, bytearray(n) is the same in both Python 2 and Python 3.
> Changing it in Python 3 increases the gulf between the two.
> The further we let Python 3 diverge from Python 2, the less likely that
> people will convert their code and the harder you make it to write code
> that runs under both.
> FWIW, I've been teaching Python full time for three years.  I cover the
> use of bytearray(n) in my classes and not a single person out of 3000+
> engineers have had a problem with it.   I seriously question the PEP's
> assertion that there is a real problem to be solved (i.e. that people
> are baffled by bytearray(bufsiz)) and that the problem is sufficiently
> painful to warrant the headaches that go along with API changes.
> The other proposal to add bytearray.byte(3) should probably be named
> bytearray.from_byte(3) for clarity.  That said, I question whether there is
> actually a use case for this.   I have never seen seen code that has a
> need to create a byte array of length one from a single integer.
> For the most part, the API will be easiest to learn if it matches what
> we do for lists and for array.array.
> Sorry Nick, but I think you're making the API worse instead of better.
> This API isn't perfect but it isn't flat-out broken either.   There is some
> unfortunate asymmetry between bytes() and bytearray() in Python 2,
> but that ship has sailed.  The current API for Python 3 is pretty good
> (though there is still a tension between wanting to be like lists and like
> strings both at the same time).
> Raymond
> P.S.  The most important problem in the Python world now is getting
> Python 2 users to adopt Python 3.  The core devs need to develop
> a strong distaste for anything that makes that problem harder.

For the record I’ve had all of the problems that Nick states and I’m
+1 on this change.

Donald Stufft
PGP: 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA

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