[issue23541] Re module's match() fails to halt on a particular input

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Minimal example for your case is

re.match(r'(\w+\s*)+\s+\d+', 'Compiling Regular Patterns to Sequential Machines')

It doesn't halt, it just needs too long time to finish. Your should rewrite the regular expression to avoid catastrophic backtracking (http://www.regular-expressions.info/catastrophic.html). For example rewrite the start of your expression as

re.match(r'\w[\w\s]*\s\d+', 'Compiling Regular Patterns to Sequential Machines')

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nosy: +serhiy.storchaka

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