Bobby Xiao <nneon...@gmail.com> added the comment:
Well, in this example the group (ar) is unmatched, so sre throws the
error, and because of the alternation, the workaround you mentioned
doesn't seem to directly apply.
A better example is probably
re.sub("foo(?:b(ar)|foo)","\\1","foofoo")
because this can't be simply repaired by refactoring the regex.
The correct behaviour, as I have observed in other regex
implementations, is to replace the group by the empty string; for
example, in Javascript:
>>> 'foobar'.replace(/foo(?:b(ar)|baz)/,'$1')
"ar"
>>> 'foobaz'.replace(/foo(?:b(ar)|baz)/,'$1')
""
----------
versions: +Python 2.5, Python 2.6, Python 3.0
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue1519638>
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