import re
p = re.compile(r'(\[[^\[\]]*\[.*?\][^\]\[]*\])', re.MULTILINE)
test_str = "[[1,2,3],[3,5,3],[9,8,9]] aoeu [5,6,9] aoeu [[4,5,5]] [[1,2,3],[3,5,3],3]\n[[1,2,3],4,[3,5,3],3]\n[1,2,3,[3,5,3],3]\n[1,2]"
 
print(re.findall(p, test_str))