Tim Peters added the comment:
BTW, note that the idea "successful lookaround assertions match an empty
string" isn't just a figure of speech: it's the literal truth, and - indeed -
is key to understanding what happens here. You can see this by adding some
capturing groups around the assertions. Like so:
m = re.search("((?<=a))((?<=a))((?<=a))((?<=a))b", "xab")
Then
[m.span(i) for i in range(1, 5)]
produces
[(2, 2), (2, 2), (2, 2), (2, 2)]
That is, each assertion matched (the same) empty string immediately preceding
"b" in the target string.
This makes perfect sense - although it may not be useful. So I think this
report should be closed with "so if it bothers you, don't do it" ;-)
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue14460>
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