Title: PyBuffer_FillInfo returns 'B' buffer, whose behavior has changed w.r.t. 3.1/3.2
Type: behavior Stage: resolved
Components: Versions: Python 3.3, Python 3.4
Status: closed Resolution: duplicate
Dependencies: Superseder: memoryviews and ctypes
View: 15944
Assigned To: Nosy List: piro, skrah, vstinner
Priority: normal Keywords: 3.3regression

Created on 2012-10-11 23:08 by piro, last changed 2013-03-23 13:07 by skrah. This issue is now closed.

Messages (3)
msg172710 - (view) Author: Daniele Varrazzo (piro) * Date: 2012-10-11 23:08
Definitely related to this change in Python 3.3:

    Accessing a memoryview element with format ‘B’ (unsigned bytes) now 
    returns an integer (in accordance with the struct module syntax). 
    For returning a bytes object the view must be cast to ‘c’ first.

The object returned by PyBuffer_FillInfo is 'B' format: this means that python code finds itself dealing in Py 3.3 with a different object respect to what returned in Py 3.1 and 3.2. Is this change in the behavior wanted? Wouldn't have been better having FillInfo return a 'c' buffer instead?

I'm adding support to Py 3.3 to psycopg2 and the B buffers make the test suite fail. I want psycopg to return consistent objects across 3.x. Is the change in this commit correct?

Is this a good way to return a 'c' buffer?
msg185044 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2013-03-23 12:55
@skrah: ping!

@piro: can't you modify psycopg2 to add conditional code depending on the Python version? IMO the behaviour change is wanted.
msg185046 - (view) Author: Stefan Krah (skrah) * (Python committer) Date: 2013-03-23 13:07
I've corresponded privately with Daniele Varrazzo about the psycopg2
issue already and then forgot about this (the psycopg2 fix is good).

Yes, the change was intentional. There's one open issue (#15944)
where dabeaz isn't happy about the change, so let's make that a
Date User Action Args
2013-03-23 13:07:43skrahsetstatus: open -> closed
superseder: memoryviews and ctypes
messages: + msg185046

resolution: duplicate
stage: resolved
2013-03-23 12:55:16vstinnersetnosy: + vstinner
messages: + msg185044
2012-10-11 23:50:08pitrousetkeywords: + 3.3regression
nosy: + skrah

versions: + Python 3.4
2012-10-11 23:08:17pirocreate