[Python-Dev] Zero-width matching in regexes
python at mrabarnett.plus.com
Mon Dec 4 18:21:09 EST 2017
I've finally come to a conclusion as to what the "correct" behaviour of
zero-width matches should be: """always return the first match, but
never a zero-width match that is joined to a previous zero-width match""".
If it's about to return a zero-width match that's joined to a previous
zero-width match, then backtrack and keep on looking for a match.
>>> print([m.span() for m in re.finditer(r'|.', 'a')])
[(0, 0), (0, 1), (1, 1)]
re.findall, re.split and re.sub should work accordingly.
If re.finditer finds n matches, then re.split should return a list of
n+1 strings and re.sub should make n replacements (excepting maxsplit,
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