New submission from kleshni <kles...@protonmail.ch>:
Hello. The following code hangs:
import fnmatch
fnmatch.fnmatchcase("a" * 32, "*" * 16 + "b")
Measurements show that its execution time rises exponentially with the number
of asterisks. Bash and SQLite 3 process this glob instantly.
This is because "fnmatchcase" generates a regular expression with repeated dots:
(?s:.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*b)\\Z
It's equivalent to:
(?s:.*b)\\Z
But works in exponential time. So the solution is to replace multiple asterisks
with a single one, so the latter regexp is generated instead.
----------
components: Library (Lib)
messages: 367963
nosy: kleshni
priority: normal
severity: normal
status: open
title: "fnmatch" exponential execution time
type: performance
versions: Python 3.8
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue40480>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
