Replace Paticular Element Inside All Parentheses

All a specific letter, let's say 'A', needs to be replaced in all parentheses. For example, A. (AbbAAbb) .A. (bbAbbAbA) .A. (bbbbAbbbb) I want to replace all 'A' in the parenthese

Solution 1:

There is a common workaround for such situations - no unbalanced / nested parentheses (as they are) should exist. You look for As that follow a closing parenthesis without matching a parenthesis:

A(?=[^)(]*\))

Live demo

Python code:

re.sub(r"A(?=[^)(]*\))", "", str)

Solution 2:

With Python re, it is not possible to just use a plain regex, you may use a replacement callback method inside re.sub.

If you want to remove all A inside (...) you may use

re.sub(r'\([^()]+\)', lambda x: x.group().replace('A', ''), s)

Here, \([^()]+\) matches (, 1+ chars other than ( and ), and then a ), passes the match value to the lambda expression (x) and the match text is accessible via m.group() (if you define capturing groups, you may access them usign .group(n)). With a mere replace('A', ''), you achieve what you need.

See the Python demo

The same can be done with a plain regex if you use PyPi regex module:

regex.sub(r'(?<=\([^()]*)A(?=[^()]*\))', '', s)

See this Python demo.

Here, the lookarounds are used, and this works because PyPi supports infinite-width lookbehinds.