Unexpected behavior regarding `re.findall()` and different syntax for searching for the same sequence

[ketchupfan]

Bug report

Bug description:

There appears to be a bug with the findall() function in the re library in which using different syntax for search for the same sequence of strings does not produce the same results. For example, when searching a DNA sequence for a GC rich region, using re.findall("[GC]{12,}", dnaString) versus re.findall("(G|C){12,}", dnaString) produces different results:

import re

dnaString = "GCCGCGGGGGCCCCCGCGCCCGGGGATATTATAAAGGGGGGGGCCCCCCCCCCCCCCCCCCCCGC"
allGCrich = re.findall("[GC]{12,}", dnaString)
print(allGCrich)
# prints "['GCCGCGGGGGCCCCCGCGCCCGGGG', 'GGGGGGGGCCCCCCCCCCCCCCCCCCCCGC']" as desired

allGCrich = re.findall("(G|C){12,}", dnaString)
print(allGCrich)
# prints "['G', 'C']" which doesn't appear to be correct

This does not appear to occur some of the other functions in the re library—such as search()—as using re.search("(G|C){12,}", dnaString) and re.search("[GC]{12,}", dnaString) produces the same results, as desired.

CPython versions tested on:

3.14

Operating systems tested on:

macOS

[StanFromIreland]

This is not a bug, you have a capturing group, as noted in the docs:

The result depends on the number of capturing groups in the pattern. If there are no groups, return a list of strings matching the whole pattern. If there is exactly one group, return a list of strings matching that group. If multiple groups are present, return a list of tuples of strings matching the groups.