How can i retain specific characters in a sentence

Question

I want to remove certain words or characters from a sentence with some exceptions using regular expression.

For example- I have a string this is [/.] a string [ra] with [/] something , I want to remove [ra] , [/.] but not [/] .

I used:

m = re.sub('\[.*?\]','',n)

which works fine, how can I retain this-> [/]

Answer 1

You may use

re.sub(r'\[(?!/])[^][]*]', '', n)

See the regex demo .

Details

• \\[ - a [ char
• (?!/]) - a negative lookahead that fails the match if there is /] immediately to the right of the current location
• [^][]* - 0+ chars other than [ and ]
• ] - a ] char.

Answer 2

Use this pattern \\[(?!\\/\\])[^\\]]+\\] and replace all matches with empty string.

Explanation: it matches [ with \\[ , then it assures, that what follows is NOT \\] , so we don't match [\\] , it's done with negative lookahead: (?!\\/\\]) , then it matches everything until ] and ] itself with pattern [^\\]]+\\] ( [^\\]]+ matches one or more characters other then ] ).

Demo

Answer 3

You could use an alternation to capture in a group what you want to keep and match what you want to remove.

result = re.sub(r"(\[/])|\[[^]]+\]", r"\1", n)

Explanation

(\\[/])|\\[[^]]+\\]

• (\\[/]) Capture [/] in a group
• | Or
• \\[[^]]+\\] Match an opening square bracket until a closing square bracket using a negated character class

Replace with the first capturing group \\1

Regex demo

Python demo