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Describe non-recursive re

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Andrew M. Kuchling 2004-08-31 12:07:43 +00:00
parent b07aae28c5
commit ab77822826
1 changed files with 13 additions and 4 deletions
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17
Doc/whatsnew/whatsnew24.tex
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@ -1184,18 +1184,27 @@ not it's a symbolic link. This differs from the existing
\item The regular expression language accepted by the \module{re} module \item The regular expression language accepted by the \module{re} module
was extended with simple conditional expressions, written as was extended with simple conditional expressions, written as
\code{(?(\var{group})\var{A}|\var{B})}. \var{group} is either a \regexp{(?(\var{group})\var{A}|\var{B})}. \var{group} is either a
numeric group ID or a group name defined with \code{(?P<group>...)} numeric group ID or a group name defined with \regexp{(?P<group>...)}
earlier in the expression. If the specified group matched, the earlier in the expression. If the specified group matched, the
regular expression pattern \var{A} will be tested against the string; if regular expression pattern \var{A} will be tested against the string; if
the group didn't match, the pattern \var{B} will be used instead. the group didn't match, the pattern \var{B} will be used instead.
\item The \module{re} module is also no longer recursive, thanks
to a massive amount of work by Gustavo Niemeyer. In a recursive
regular expression engine, certain patterns result in a large amount
of C stack space being consumed, and it was possible to overflow the
stack. For example, if you matched a 30000-byte string of \samp{a}
characters against the expression \regexp{(a|b)+}, one stack frame was
consumed per character. Python 2.3 tried to check for stack overflow
and raise a \exception{RuntimeError} exception, but if you were
unlucky Python could dump core. Python 2.4's regular expression
engine can match this pattern without problems.
\item A new \function{socketpair()} function was added to the \item A new \function{socketpair()} function was added to the
\module{socket} module, returning a pair of connected sockets. \module{socket} module, returning a pair of connected sockets.
(Contributed by Dave Cole.) (Contributed by Dave Cole.)
% XXX sre is now non-recursive.
\item The \function{sys.exitfunc()} function has been deprecated. Code \item The \function{sys.exitfunc()} function has been deprecated. Code
should be using the existing \module{atexit} module, which correctly should be using the existing \module{atexit} module, which correctly
handles calling multiple exit functions. Eventually handles calling multiple exit functions. Eventually