Extract and sort all numbers that appear after ',
re.findall() behaves differently depending on whether the regex contains capturing parentheses.  If it doesn't contain capturing parentheses, then it just returns the matching text as a flat list.

So, how can you avoid capturing?  Just rewrite your regex to use a positive lookbehind assertion.

s = "'bhhd',12 'kjubk',2 'bjki',98 'khjbjj',4"
all = re.findall(r"(?&lt;=',)\d+", s)
print(",".join(sorted(all, key=int)))