How to remove a line based on a regular expression with exceptions

Question

I need to remove lines that have the following characteristics.

...

As you can see, the number that is found after the word index and after the _ and also, the image format (png, jpg) varies.

I need to generate a regex that removes all these lines EXECPTING numbers found after the index. For example, I need to keep the lines that have only the numbers 1 and 2.

I have the following generated regular expression

^
$

but wanting to keep the numbers 1 and 2, it also keeps the numbers 22, 23, 100 and 1000 since they contain those numbers

user_11329890 · Answer

Use

^
$

See regex proof. Use $1 as replacement.

EXPLANATION

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  
                    '>
'
--------------------------------------------------------------------------------
  $                        before an optional 
, and the end of the
                           string

user_1565512 · Answer

Instead of using the negative lookahead (?!2|1) you could use

(?![12]_)

which prevents a match if the next character is 1 or 2 followed by an underscore.

user_12497813 · Answer

By fiddling around here, I think I got what you are looking for:

import re

txt = "index-4_8.jpg"
txt2 = "index-1_8.png"

#Check if the string starts with "The":

x = re.search("^(index-2_|index-1_).+(.jpg|.png)$", txt)

if (x):
    print('Matched')
else:
    print('NotMatched')

x = re.search("^(index-2_|index-1_).+(.jpg|.png)$", txt2)

if (x):
    print('Matched')
else:
    print('NotMatched')

How to remove a line based on a regular expression with exceptions

3 Answers