python - How to count consecutive repetitions of a substring in a string?

Question

I need to find consecutive (non-overlapping) repetitions of a substring in a string. I can count them but not consecutive. For instance:

string = "AASDASDDAAAAAAAAERQREQREQRAAAAREWQRWERAAA"
substring = "AA"

here, "AA" is repeated one time at the beginning of the string, then 4 times, then 2 times, etc. I should select the biggest one, in this example - 4 times.

How can I do that?

Answer 1

Regular expressions shine when searching through strings. Here you can find all groups of one or more AA with (?:AA)+ the (?: simply tells the engine to interpret the parentheses for grouping only.

Once you have the groups you can use max() to find the longest based on length (len()).

import re

s = "AASDASDDAAAAAAAAERQREQREQRAAAAREWQRWERAAA"

groups = re.findall(r'(?:AA)+', s)
print(groups)
# ['AA', 'AAAAAAAA', 'AAAA', 'AA']

largest = max(groups, key=len)
print(len(largest) // 2)
# 4