[New-bugs-announce] [issue39195] re._compile should check if the argument is a compiled pattern before checking cache and flags

[Recursing]

New submission from Recursing <buonanno.lorenzo at gmail.com>:

In the re module, re._compile gets called when using most re methods.
In my use case (which I think is not rare) I have a small number of compiled patterns that I have to match against a large number of short strings

profiling showed that half of the total runtime was still spent in re._compile, checking for the type of the flags and trying to get the pattern in a cache

Example code that exhibits this behavior:

import re

pattern = re.compile("spam")
string = "Monty pythons"
for _ in range(1000000):
    re.search(pattern, string)

----------
components: Library (Lib)
messages: 359210
nosy: Recursing
priority: normal
severity: normal
status: open
title: re._compile should check if the argument is a compiled pattern before checking cache and flags
type: performance
versions: Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39195>
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