Josh Rosenberg <shadowranger+python@gmail.com> added the comment: The definition of \w, historically, has corresponded to the set of characters that can occur in legal variable names in C (alphanumeric ASCII plus underscores, making it equivalent to [a-zA-Z0-9_] for ASCII regex). That's why, on top of the definitely wordy alphabetic characters, and the arguably wordy numerics, it includes the underscore, _. That definition predates Unicode entirely, and Python is just building on it by expanding the definition of "alphanumeric" to encompass all alphanumeric characters in Unicode. We definitely can't remove underscores from the definition without breaking existing code which assumes a common subset of PCRE support (every regex flavor I know of includes underscores in \w). Adding the zero width characters seems of limited benefit (especially in the non-joiner case; if you're trying to pull out words, presumably you don't want to group letters across a non-joining boundary?). Basically, you're parsing "Unicode word characters" as "Unicode's definition of word characters", when it's really meant to mean "All word characters, not just ASCII". You omitted the clarifying remarks from the documentation though, the full description is:
Matches Unicode word characters; this includes most characters that can be part of a word in any language, as well as numbers and the underscore. If the ASCII flag is used, only [a-zA-Z0-9_] is matched.
That's about as precise as I think we can make it (because technically, some of the things that count as "word characters" aren't actually part of an "alphabet" in the technical definition). If you think there is a clearer way of expressing it, please suggest a better phrasing, and this can be fixed as a documentation bug. ---------- nosy: +josh.r _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue38566> _______________________________________