Why do the following two python split function calls generate difference result? (From here: https://docs.python.org/3/library/re.html#contents-of-module-re)
re.split(r'\W+', 'Words, words, words.')
['Words', 'words', 'words', '']
re.split(r'(\W+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '']