regex error : raise error, v # invalid expression

Question

I have a variable device='A/B/C/X1' that is commented out in another file. There can be multiple instances of the same device such as 'A/B/C/X1@1', ..@2 and so on. All of these devices are commented out in another file with a prefix *.

I want to remove the * but not affect similar devices like 'A/B/C/X**10**'.

I tried using regex to simply substitute a pattern using the following line of code, but I'm getting an InvalidExpression error.

line=re.sub('^*'+device+'@',device+'@',line)

Please help.

Martin Valgur · Answer 1 · 2017-01-25T19:02:12.320

3

You need to escape the asterisk since it has a meaning in regex syntax: line=re.sub(r'^\*'+device+'@',device+'@',line).

Escaping the variables you use to construct the regex is also always a good idea: line=re.sub(r'^\*'+re.escape(device)+'@',device+'@',line)

edited Jan 25 '17 at 19:02

answered Jan 25 '17 at 18:59

Martin Valgur

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Or put a r in front of your regex string – Emaro Jan 25 '17 at 19:01
For the record it has a special meaning in markdown too OP. That's why you had random italics and bolded text all over the place. – Tagc Jan 25 '17 at 19:02
@Emaro That will not be sufficient since it will only disable unescaping of backslashes in that string, nothing more. – Martin Valgur Jan 25 '17 at 19:04
Thanks guys, got it. – Sarthak Singhal Jan 27 '17 at 01:59

score 0 · Answer 2 · edited Jun 06 '18 at 11:53

0

def replace_all(text):
    if text in ['*']:
        text = text.replace(text, '')
    return text

my_text = 'adsada*asd*****dsa*****'

result = "".join(map(replace_all, my_text))
print result

Or

import re
my_text = 'adsada*asd*****dsa*****'
print (re.sub('\*', '', my_text))

edited Jun 06 '18 at 11:53

4b0

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answered Jun 06 '18 at 11:51

Tim Uzlov

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regex error : raise error, v # invalid expression

2 Answers2

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