# Add "re.prefixmatch()", deprecate "re.match()"

**URL:** <https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927>\
**Category:** Python Help\
**Created:** [January 29, 2026, 1:27pm UTC](https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927 "2026-01-29T13:27:55Z")\
**Posts on this page:** 1\
**Showing post:** 9

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**Author:** ![tim.one](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/tim.one/32/282_2.png) [@tim.one](https://discuss.python.org/u/tim.one)\
**Post date:** [January 29, 2026, 11:10pm UTC](https://discuss.python.org/t/add-re-prefixmatch-deprecate-re-match/105927/9 "2026-01-29T23:10:29Z")

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Here’s an interesting rexexp that came up recently:

```
r"\d+\s+"

```

What’s the big deal? Run it with `.match()` and it returns “almost instantly” even if the target string doesn’t match.

Bur run it with `.search()` on a string like `"5" * N` (which can’t suicceed) , and it takes time _quadratic_ in `N` to fail. But `N` has to be in the thousands before this becomes very noticeable.

I don’t believe I’ve ever seen a discussion of this kind of failure mode. I’ll leave it to you to figure out why it happens 😉

This is not a case of “catastrophic backtracking” (which consumes time exponential in `N` to fail to match), it’s just a consequence of how `.search()` works. There appears to be nothing you can do to the regexp to make it fast in all cases. Using possessive `\d++` instead does speed it quite a bit, but it’s _still_ quadratic time.

Also true under the very capable `regex` extension module, which is immune to many ways to _try_ to provoke exponential time behavior. It’s no faster in this case than the core’s `re` module.

Personally, I almost always use “match” instead of “search”. But then I don’t use regexps to try to do “too much” at a time. I use it more like a flexible lexer, to pick off “the next” token in an input string, typically passing a “start index” argument too to a compiled pattern.

Deprecating `match` would just annoy people like me a lot 😉

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