s = ['Hello', 'world', '!', 'How', 'are', 'you', '?', 'Have', 'a', 'good',
    'day', '.']
final = []
b = []
for x in s:
    b.append(x)
if x in ('.', '?', '!', '\n'):
    final.append(b)
b = []
Python: List containing sublist of strings