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Issues #814253, #9179: Warnings now are raised when group references and

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conditional group references are used in lookbehind assertions in regular
expressions.
This commit is contained in:
Serhiy Storchaka 2015-02-21 12:08:52 +02:00
parent a1543cdcd6
commit a3369a524c
4 changed files with 61 additions and 3 deletions
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7
Doc/library/re.rst
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@ -281,7 +281,9 @@ The special characters are:
assertion`. ``(?<=abc)def`` will find a match in ``abcdef``, since the
lookbehind will back up 3 characters and check if the contained pattern matches.
The contained pattern must only match strings of some fixed length, meaning that
``abc`` or ``a|b`` are allowed, but ``a*`` and ``a{3,4}`` are not. Note that
``abc`` or ``a|b`` are allowed, but ``a*`` and ``a{3,4}`` are not. Group
references are not supported even if they match strings of some fixed length.
Note that
patterns which start with positive lookbehind assertions will not match at the
beginning of the string being searched; you will most likely want to use the
:func:`search` function rather than the :func:`match` function:
@ -301,7 +303,8 @@ The special characters are:
Matches if the current position in the string is not preceded by a match for
``...``. This is called a :dfn:`negative lookbehind assertion`. Similar to
positive lookbehind assertions, the contained pattern must only match strings of
some fixed length. Patterns which start with negative lookbehind assertions may
some fixed length and shouldn't contain group references.
Patterns which start with negative lookbehind assertions may
match at the beginning of the string being searched.
``(?(id/name)yes-pattern|no-pattern)``