Multi tool use

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How to split string into substrings of identical letters?

How do I split a string consisting of lowercase English alphabetical letters into substrings consisting of identical letters - so for an input:

"aaaabbcccdd"


The function should output a list:

["aaaa", "bb", "ccc", "dd"]


itertools.groupby

3 Answers
3

The following list comprehension using itertools.groupby and str.join will work:

itertools.groupby

str.join

from itertools import groupby

s = "aaaabbcccdd"
[''.join(g) for _, g in groupby(s)]
# ["aaaa", "bb", "ccc", "dd"]


You can use regex with a back reference:

import re
from operator import itemgetter
print(list(map(itemgetter(0), re.findall(r'((.)2*)', "aaaabbcccdd"))))


This outputs:

['aaaa', 'bb', 'ccc', 'dd']


A Counter solution -

from collections import Counter

[i*j for i, j in Counter("aaaabbcccdd").iteritems()]
# OP ["aaaa", "bb", "ccc", "dd"]


"aaaabbcccddasdffas"

['aaaaaa', 'ccc', 'bb', 'ddd', 'ff', 'ss']

'aaaaaa'

lowercase alphabetic letters into substrings consisting of identical letters

a

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