At Friday 10/11/2006 00:08, [EMAIL PROTECTED] wrote:
> > >>> import binascii
> > >>> cdb = binascii.unhexlify('%02X%06X%02X%02X' % (0x08,
0x12345, 0x80, 0))
> > >>> binascii.hexlify(cdb)
> >'080123458000'
>
> The only problem I can see is that this code is endianness-dependent;
> the suggested
> > ... Python can say six-nybble hex:
> >
> > >>> import binascii
> > >>> cdb = binascii.unhexlify('%02X%06X%02X%02X' % (0x08, 0x12345, 0x80, 0))
> > >>> binascii.hexlify(cdb)
> >'080123458000'
>
> The only problem I can see is that this code is endianness-dependent;
> the suggested versions using
At Thursday 9/11/2006 22:24, [EMAIL PROTECTED] wrote:
Perhaps Python can't concisely say three-byte int ...
But Python can say six-nybble hex:
>>> import binascii
>>> cdb = binascii.unhexlify('%02X%06X%02X%02X' % (0x08, 0x12345, 0x80, 0))
>>> binascii.hexlify(cdb)
'080123458000'
The only pro
[EMAIL PROTECTED] wrote:
> Speaking as the OP, perhaps I should mention:
>
> > > [-3:] to [1:] is a minor cosmetic improvement
>
> To my eye, that's Not an improvement.
>
> '\x08' '\x01\x23\x45' '\x80' '\0' is the correct pack of (0x08,
> 0x12345, 0x80, 0) because '\x01\x23\x45' are the significan
[EMAIL PROTECTED] wrote:
>
> Pack ' these things.
>
> The people who wrote this stuff forty years ago were thinking of bit
> fields - here bit lengths of 8 then 3 then 21 then 8 then 8 bits -
> cheating only when the bit boundaries happened to hit byte boundaries.
>
> Yes, as you describe in thi
Perhaps Python can't concisely say three-byte int ...
But Python can say six-nybble hex:
>>> import binascii
>>> cdb = binascii.unhexlify('%02X%06X%02X%02X' % (0x08, 0x12345, 0x80, 0))
>>> binascii.hexlify(cdb)
'080123458000'
>>>
Thanks again for patiently helping me find this. A shortcut is:
[EMAIL PROTECTED] wrote:
> > "struct" == "Python struct module"
> >
> > Struct module has (concise) codes B, H, I, Q for unsigned integers of
> > lengths 1, 2, 4, 8, but does *not* have a code for 3-byte integers.
>
> I thought that's what the manual meant, but I was unsure, thank you.
If it does
Speaking as the OP, perhaps I should mention:
> > [-3:] to [1:] is a minor cosmetic improvement
To my eye, that's Not an improvement.
'\x08' '\x01\x23\x45' '\x80' '\0' is the correct pack of (0x08,
0x12345, 0x80, 0) because '\x01\x23\x45' are the significant low three
bytes of a big-endian x1234
> > when talking the 1960's lingo
> > ...
> > X12Inquiry = 0x12
> > xxs = [0] * 6
> > xxs[0] = X12Inquiry
> > xxs[4] = allocationLength
> > rq = ''.join([chr(xx) for xx in xxs])
>
> It looks wrong (and a few other adjectives),
Ah, we agree, thank you for saying.
> Looks like little-endian 4-byte
> "struct" == "Python struct module"
>
> Struct module has (concise) codes B, H, I, Q for unsigned integers of
> lengths 1, 2, 4, 8, but does *not* have a code for 3-byte integers.
I thought that's what the manual meant, but I was unsure, thank you.
> > > 1. Not as concisely as a one-byte struct
> Help, what did you mean by the question?
How does Python express the idea:
i) Produce the six bytes '\x08' '\x01\x23\x45' '\x80' '\0' at run-time
when given the tuple (0x08, 0x12345, 0x80, 0).
ii) Produce the six bytes '\x12' '\0\0\0' '\x24' '\0' when given the
tuple (0x12, 0, 0x24, 0).
iii)
[EMAIL PROTECTED] wrote:
> > Not as concisely as a one-byte struct code
>
> Help, what do you mean?
Help, what did you mean by the question?
"struct" == "Python struct module"
Struct module has (concise) codes B, H, I, Q for unsigned integers of
lengths 1, 2, 4, 8, but does *not* have a code for
> > > cdb0 = '\x08' '\x01\x23\x45' '\x80' '\0'
> >
> > cdb = ''
> > cdb += struct.pack('>B', 0x08)
> > cdb += struct.pack('>I', skip)[-3:]
> > cdb += struct.pack('>BB', count, 0)
>
> The change from [-3:] to [1:] is a minor cosmetic improvement,
Ouch, [1:] works while sizeof I is 4, yes, but that'
> Not as concisely as a one-byte struct code
Help, what do you mean?
> you presumably... read... the manual ...
Did I reread the wrong parts? I see I could define a ctypes.Structure
since 2.5, but that would be neither concise, nor since 2.3.
> when 24-bit machines become ... popular
Indeed t
Dave Opstad wrote:
> Sorry, that should have been:
>
> cdb += struct.pack(">L", skip)[1:]
>
">L" and ">I" produce exactly the same 4-byte result. The change from
[-3:] to [1:] is a minor cosmetic improvement, but obscures the
underlying ... a bit like putting mascara on a pig. I got the
impressio
Sorry, that should have been:
cdb += struct.pack(">L", skip)[1:]
Dave
--
http://mail.python.org/mailman/listinfo/python-list
In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] wrote:
> Can Python not express the idea of a three-byte int?
>
> For instance, in the working example below, can we somehow collapse the
> three calls of struct.pack into one?
>
> >>> import struct
> >>>
> >>> skip = 0x123456 ; count = 0x80
> >
[EMAIL PROTECTED] wrote:
> Can Python not express the idea of a three-byte int?
It is a bit hard to determine what that (rhetorical?) question means.
Possible answers:
1. Not as concisely as a one-byte struct code -- as you presumably have
already determined by reading the manual ...
2. No, but wh
18 matches
Mail list logo
