import re
regex = r"\[[^][]*]|\b(hello)\b"
test_str = ("hello world [hello hello] world hello [world hello world hello] world hello [hello] hello")
print(list(filter(None, re.findall(regex, test_str))))
aW1wb3J0IHJlCgpyZWdleCA9IHIiXFtbXl1bXSpdfFxiKGhlbGxvKVxiIgoKdGVzdF9zdHIgPSAoImhlbGxvIHdvcmxkIFtoZWxsbyBoZWxsb10gd29ybGQgaGVsbG8gW3dvcmxkIGhlbGxvIHdvcmxkIGhlbGxvXSB3b3JsZCBoZWxsbyBbaGVsbG9dIGhlbGxvIikKCnByaW50KGxpc3QoZmlsdGVyKE5vbmUsIHJlLmZpbmRhbGwocmVnZXgsIHRlc3Rfc3RyKSkpKQ==