I am using regex to classify special numbers.

The pattern I wish to match looks like this : 5ABCDXXYY.

Its a number that:

• starts with "5"
• followed by 4 different digits (ABCD)
• then 2 matching digits (XX)
• and again 2 matching digits (YY)

examples the regex should match: 590631122, 510367722 examples the regex shouldn't match: 566781100, 519283412

I have tried the below

S_E_4_A = 590631122
S_E_4_A_pattern = re.sub(r'.{4}\d(\d)\1(\d)\2', "Special-Private", str(S_E_4_A))
print(S_E_4_A_pattern)

The problem with my regex is that it also match other patterns such as 5ABXXYYZZ.

I want to change my regex to match only two sets of repeating numbers and not more.

Thank you

You may use this regex to validate your constraints:

\b(?!.{0,3}(\w)\1)5\w{4}(\d)\2(\d)\3\b

RegEx Demo

RegEx Breakup:

• \b: Word boundary
• (?!.(\w)\1): Negative lookahead to ensure we don't have a repeat of any chat after 0 to 3 chars
• 5: Match digit 5
• \w{4}: Match 4 word characters
• (\d): Match a digit in capture group #2
• \2: Match same value as in capture group #2
• (\d): Match a digit in capture group #3
• \3: Match same value as in capture group #3
• \b: Word boundary