import re
words = ['session', 'curl']
month = 'Dec'
x = '|'.join([re.escape(w) for w in words])
m = re.search(r'^(?!.*({})).*{}'.format(x, month), 'Date: Dec 2016')
if m:
print('Matched')
aW1wb3J0IHJlCndvcmRzID0gWydzZXNzaW9uJywgJ2N1cmwnXQptb250aCA9ICdEZWMnCnggPSAnfCcuam9pbihbcmUuZXNjYXBlKHcpIGZvciB3IGluIHdvcmRzXSkKbSA9IHJlLnNlYXJjaChyJ14oPyEuKih7fSkpLip7fScuZm9ybWF0KHgsIG1vbnRoKSwgJ0RhdGU6IERlYyAyMDE2JykKaWYgbToKCXByaW50KCdNYXRjaGVkJyk=