# 'adsfdsa[aa] sadfbdsaf[bb], [cc]' => [aa, bb, cc]

import re

str = 'adsfdsa[aa] sadfbdsaf[bb], [cc]'

list = re.findall("\[\w+\]", str)       # ['[aa]', '[bb]', '[cc]']
list = map(lambda x: x[1:-1], list)     # ['aa', 'bb', 'cc']

print(list)