import re
s1 = 'Arithmetic Return 2018 (%)'
s2 = 'Arithmetic Return 2019 (%)'
p = re.compile(r'^.*?Arithm.*$')
w = [p.findall(a) for a in [s1, s2]]
print(w)
aW1wb3J0IHJlCnMxID0gJ0FyaXRobWV0aWMgUmV0dXJuIDIwMTggKCUpJwpzMiA9ICdBcml0aG1ldGljIFJldHVybiAyMDE5ICglKScKCnAgPSByZS5jb21waWxlKHInXi4qP0FyaXRobS4qJCcpCncgPSBbcC5maW5kYWxsKGEpIGZvciBhIGluIFtzMSwgczJdXQpwcmludCh3KQ==