Python - Find Sequence Of Same Characters

I'm trying to use regex to match sequences of one or more instances of the same characters in a string. Example : string = '55544355' # The regex should retrieve sequences '555',

Solution 1:

You can use re.findall() and the ((.)\2*) regular expression:

>>> [item[0] for item in re.findall(r"((.)\2*)", string)]
['555', '44', '3', '55']

the key part is inside the outer capturing group - (.)\2*. Here we capture a single character via (.) then reference this character by the group number: \2. The group number is 2 because we have an outer capturing group with number 1. * means 0 or more times.

You could've also solved it with a single capturing group and re.finditer():

>>> [item.group(0) for item in re.finditer(r"(.)\1*", string)]
['555', '44', '3', '55']

Solution 2:

You can do this easily without regex using itertools.groupby:

>>> from itertools import groupby
>>> s = '55544355'>>> [''.join(g) for _, g in groupby(s)]
['555', '44', '3', '55']

Solution 3:

Probably not the best option here, but for the sake of variety, how about this logic:

>>> deff(s):
        l = []
        c = s[0]
        for x in s:
            if x in c:
                c += x
                continue
            l.append(c)
            c = x
        l.append(c)
        return l

>>> f('55544355')
['555', '44', '3', '55']
>>> f('123444555678999001')
['1', '2', '3', '444', '555', '6', '7', '8', '999', '00', '1']