Regex on bytes in Python

Question

I would like to extract 10.00ML in following byte: b'\x0200S10.00ML\x03' So I've tried extracting the 10.00ML between 200S and \x03:

result = re.search(b'200S(.*)x03', b'\x0200S10.00ML\x03')

which didn't work, no element was found:

AttributeError: 'NoneType' object has no attribute 'group'

Using only strings I have a minimum working example:

test_string = 'a3223b'
result = re.search('a(.*)b', test_string)
print(result.group(1))

The characters x03 do not actually appear in that string, that's just part of an escape sequence. You would need the preceding backslash as well. — jasonharper
– jasonharper, Commented Apr 28, 2022 at 13:30

Wiktor Stribiżew · Accepted Answer · 2022-04-28 13:29:36Z

5

You can use

import re
text = b'\x0200S10.00ML\x03'
m = re.search(rb'\x0200S(.*?)\x03', text, re.S)
if m:
    print( m.group(1).decode('utf-8') )

# => 10.00ML

Note that \x02 and \x03 are START OF HEADING and START OF TEXT control chars, so you cannot match them as literal text.

answered Apr 28, 2022 at 13:29

Wiktor Stribiżew

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