I find the following inconsistent:
===
 >>> sys.version
'2.4.1a0 (#2, Feb  9 2005, 12:50:04) \n[GCC 3.3.5 (Debian 1:3.3.5-8)]'
 >>> pack('>B', 256)
'\x00'
 >>> pack('<B', 256)
'\x00'
 >>> pack('B', 256)
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
struct.error: ubyte format requires 0<=number<=255
 >>>
===

I was hoping that '>B' and '<B' would raise an exception,
ust as 'B' does.

On Oct 27 2006, 11:17 am, Jansson Christer reported a
different anomoly to this newsgroup, using the same
subject.

Python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit
(Intel)] on win
32
| >>> from struct import pack
| >>> pack('<B', 256)
| __main__:1: DeprecationWarning: 'B' format requires 0 <= number <=
255
| '\x00'

Until the deprecation warning becomes an exception in 2.6, I'd suggest
doing your own checking:
assert 0 <= pack_B_candidate <= 255