It’s a design decision that was made, and could have gone either way. Tim Peters made this post to explain:
For example, if you split “abc” by the pattern x*, what do you
expect? The pattern matches (with length 0) at 4 places,
but I bet most people would be surprised to get[”, ‘a’, ‘b’, ‘c’, ”]
back instead of (as they do get)
[‘abc’]
Some others disagree with him though. Guido van Rossum doesn’t want it changed due to backwards compatibility issues. He did say:
I’m okay with adding a flag to enable this behavior though.
Edit:
There is a workaround posted by Jan Burgy:
>>> s = "Split along words, preserve punctuation!"
>>> re.sub(r"\s+|\b", '\f', s).split('\f')
['', 'Split', 'along', 'words', ',', 'preserve', 'punctuation', '!']
Where '\f'
can be replaced by any unused character.