How to capture the sets of repeating characters in Python regex

Question

import re

line = "..12345678910111213141516171820212223"

regex = re.compile(r'((?:[a-zA-Z0-9])\1+)')

print ("not coming here")

matches = re.findall(regex,line)

print (matches)

In the above code i am trying to capture the groups of repeating characters.

So for example i need the answers like :
111
222
etc.

But when i run the above code i get this error:

Traceback (most recent call last):

  File "First.py", line 3, in <module>

    regex = re.compile(r'((?:[a-zA-Z0-9])\1+)')

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\re.py", lin

e 224, in compile

    return _compile(pattern, flags)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\re.py", lin

e 293, in _compile

    p = sre_compile.compile(pattern, flags)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_compile

.py", line 536, in compile

    p = sre_parse.parse(p, flags)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 829, in parse

    p = _parse_sub(source, pattern, 0)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 437, in _parse_sub

    itemsappend(_parse(source, state))

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 778, in _parse

    p = _parse_sub(source, state)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 437, in _parse_sub

    itemsappend(_parse(source, state))

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 524, in _parse

    code = _escape(source, this, state)

  File "C:\Users\bhatsubh\AppData\Local\Programs\Python\Python35\lib\sre_parse.p

y", line 415, in _escape

    len(escape))

sre_constants.error: cannot refer to an open group at position 16

Someone please guide me where i am going wrong.

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Answer 1

You (probably) want

([a-zA-Z0-9])\1+

See a demo on regex101.com.

In Python:

import re
line = "..12345678910111213141516171820212223"
regex = re.compile(r'([a-zA-Z0-9])\1+')

matches = [match.group(0) for match in regex.finditer(line)]
print (matches)
# ['111', '222']

How to capture the sets of repeating characters in Python regex

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