struct.pack oddity

Erik Johnson nobody at invalid.com
Tue Mar 13 17:55:54 CET 2007


"Dave Opstad" <dave.opstad at monotypeimaging.com> wrote in message
news:45f6bd4a$0$6972$afc38c87 at ...
> Is the lack of a struct.error when the byte-order mark is at the start
> of the format intentional? This seems like a bug to me, but maybe
> there's a subtlety here I'm not seeing.

    I am by no means any sort of expert on this module, but for what it's
worth, the behaviour is basically the same for my Python 2.4.3 under Cygwin
(except that there is no deprecation warning) and I agree with you: this
seems like a bug to me. Or maybe not technically a bug, but the behaviour
could be improved. I would expect to get the same struct.error in all three
cases:

$ python
Python 2.4.3 (#1, May 18 2006, 07:40:45)
[GCC 3.3.3 (cygwin special)] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from struct import *
>>> pack('H', 100000)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
struct.error: short format requires 0<=number<=USHRT_MAX
>>> pack('>H', 100000)
'\x86\xa0'
>>> pack('<H', 100000)
'\xa0\x86'
>>>

    There used to be a form at the bottom left of the main site:
www.python.org for reporting bugs, but that now seems to be used only for
reporting stuff about the web site itself.  The struct module comes from
struct.dll, so I can't see any comments about who wrote or maintains that
module.

    Barring anyone else disagreeing with classifying it as a bug, I would
suggest reporting it. Proper procedure for reporting a bug appears to be
covered in section B of the Python Library Reference:
http://docs.python.org/lib/reporting-bugs.html

Hope that helps,
-ej





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