octet string conversion

Bengt Richter bokr at oz.net
Tue Jul 29 05:31:05 CEST 2003


On 28 Jul 2003 13:14:50 -0700, ruach at chpc.utah.edu (Matthew) wrote:

>I am working on some software that uses SNMP to get information from
>routers and switches. I am using the pysnmp module (v2.0.8) to do the
>snmp part. The problem that I am having is that when I query a router
>for mac addresses pysnmp returns octetstrings like this:
>
>\000\002\263\254\264\351
>\010\000 \301F\021
>\010\000 \300\303[
>\000\002\263\254\264\241
>
>what I need though is hex strings like this:
>
>0:e0:7d:de:5:48
>0:e0:7d:c8:dc:9f
>8:0:36:4:3b:de
>0:80:ad:3a:9e:2b
>
>Can anyone tell me how to convert the octet strings to hex strings?
>
Assuming that your data is really octal character representations like \nnn,
and the spaces, F, and [ in the middle lines are typos, and that your need example
has nothing to do with the example data,

 >>> data = r"""
 ... \000\002\263\254\264\351
 ... \010\000\301\021
 ... \010\000\300\303
 ... \000\002\263\254\264\241
 ... """
 >>> for line in data.splitlines():
 ...     if not line: continue   # skip the first \n in data above
 ...     print 'line: %r' %line
 ...     oct3list = line.split('\\')[1:]
 ...     print 'oct3list: %r'%oct3list
 ...     octvals = [int(oct3,8) for oct3 in oct3list]
 ...     print 'octvals: %r'%octvals
 ...     hexstrings = ['%02X'%octval for octval in octvals]
 ...     print 'hexstrings: %r'%hexstrings
 ...     print 'joined with colons => %r' % ':'.join(hexstrings)
 ...     print
 ...
 line: '\\000\\002\\263\\254\\264\\351'
 oct3list: ['000', '002', '263', '254', '264', '351']
 octvals: [0, 2, 179, 172, 180, 233]
 hexstrings: ['00', '02', 'B3', 'AC', 'B4', 'E9']
 joined with colons => '00:02:B3:AC:B4:E9'  

 line: '\\010\\000\\301\\021'
 oct3list: ['010', '000', '301', '021']
 octvals: [8, 0, 193, 17]
 hexstrings: ['08', '00', 'C1', '11']
 joined with colons => '08:00:C1:11'

 line: '\\010\\000\\300\\303'
 oct3list: ['010', '000', '300', '303']
 octvals: [8, 0, 192, 195]
 hexstrings: ['08', '00', 'C0', 'C3']
 joined with colons => '08:00:C0:C3'

 line: '\\000\\002\\263\\254\\264\\241'
 oct3list: ['000', '002', '263', '254', '264', '241']
 octvals: [0, 2, 179, 172, 180, 161]
 hexstrings: ['00', '02', 'B3', 'AC', 'B4', 'A1']
 joined with colons => '00:02:B3:AC:B4:A1'

and I got it wrong because I used fixed 2-char hex in upper case,
and I'm showing the repr() of the line, which doubles the \'s,
then you can fix it ;-)

And get this for the data:

 line: \000\002\263\254\264\351
 joined with colons => '0:2:b3:ac:b4:e9'

 line: \010\000\301\021
 joined with colons => '8:0:c1:11'

 line: \010\000\300\303
 joined with colons => '8:0:c0:c3'

 line: \000\002\263\254\264\241
 joined with colons => '0:2:b3:ac:b4:a1'

In future, please post actual data and corresponding output
(or if you did this time, explain the anomalies). Otherwise
it's a guessing game, and wastes all of our time except for
silly finger exercises.

Regards,
Bengt Richter




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