Regex remove occurence of alphabet in string-CodePudding

Looking for a regex that allow to remove all occurences for an character(alphabet) and let only the first occurence, for example: input string = AAAAAABBBBBBBCDEEEEAAAAAAFFFBBB output should be string = ABCDEF thanks for your help

CodePudding user response：

You can use regex but you can also use sets because set removes duplicates

First Solution:

regex = re.compile(r'\b(' remove r')\b', flags=re.IGNORECASE)

Second Solution:

string = "AAAAAABBBBBBBCDEEEEAAAAAAFFFBBB"
new_set = sorted(set(string))
print(new_set)

CodePudding user response：

You could try:

([A-Z])(?<=\1.*?\1)

See an online demo

([A-Z]) - 1st Capture group holding a single alpha-char;
(?<=\1.*?\1) - Positive lookbehind to assert position is at least preceding by a copy of itself prior to itself.

Substitute matches with empty string.

Note: Not all applications will support this type of zero-width lookbehind.