Python3 regex on bytes variable [duplicate]

Question

I'm trying to perform a regex substitution on a bytes variable but I receive the error

  sequence item 0: expected a bytes-like object, str found

Here is a small code example to reproduce the problem with python3:

import re

try:
    test = b'\x1babc\x07123'
    test = re.sub(b"\x1b.*\x07", '', test)
    print(test)
except Exception as e:
    print(e)

Note: the * quantifier is greedy: it tries to match as much as possible. For example, provided your bytestring is \x1babc\x07123\x07 the result after substitution will be empty string. Adding ? after the quantifier makes it perform the match in non-greedy or minimal fashion; as few characters as possible will be matched. (from docs.python.org/3/library/re.html) — LRDPRDX
– LRDPRDX, Commented Sep 17, 2023 at 7:38

Dimitris Fasarakis Hilliard · Accepted Answer · 2017-06-09 12:10:11Z

33

When acting on bytes object, all arguments must be of type byte, including the replacement string. That is:

test = re.sub(b"\x1b.*\x07", b'', test)

answered Jun 9, 2017 at 12:10

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Comments

Martijn Pieters · Accepted Answer · 2017-06-09 12:09:59Z

7

Your replacement value must be a bytes object too:

re.sub(b"\x1b.*\x07", b'', test)
#                     ^^^

You can't replace matching bytes with a str object, even if that is an empty string object.

Demo:

>>> import re
>>> test = b'\x1babc\x07123'
>>> re.sub(b"\x1b.*\x07", b'', test)
b'123'

answered Jun 9, 2017 at 12:09

Martijn Pieters

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