Steven D'Aprano wrote:
On Thu, 09 Apr 2009 02:56:00 -0700, David Liang wrote:
Hi all,
I'm having a weird problem with a regular expression (tested in 2.6 and
3.0):
Basically, any of these:
_re_comments = re.compile(r'^(([^\\]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
_re_comments = re.compile(r'^(([^#]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
_re_comments = re.compile(r'^(([^"]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
followed by for example,
line = r'~/.[m]ozilla/firefox/*.default/chrome'
print(_re_comments.sub(r'\1', line))
...hangs the interpreter.
I can confirm the first one hangs the interpreter in Python 2.5 as well.
I haven't tested the other two.
To my mind, this is a bug in the RE engine. Is there any reason to not
treat it as a bug?
It's not a bug but one of those pathological cases where there are a LOT
of possibilities to try (we're talking about exponential growth here).
Hmm, maybe the re module needs to let the user set a timeout control
that raises an exception if it takes longer than n seconds (it can
already be interrupted by ^C)...
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