On Thu, 27 Dec 2018 19:48:40 +0800
Ma Lin <malin...@163.com> wrote:
> We can use this literal to represent a compiled pattern, for example:
>
> >>> p"(?i)[a-z]".findall("a1B2c3")
> ['a', 'B', 'c']
>
> >>> compiled = p"(?<=abc)def"
> >>> m = compiled.search('abcdef')
> >>> m.group(0)
> 'def'
>
> >>> rp'\W+'.split('Words, words, words.')
> ['Words', 'words', 'words', '']
>
> This allows peephole optimizer to store compiled pattern in .pyc file,
> we can get performance optimization like replacing constant set by
> frozenset in .pyc file.
>
> Then such issue [1] can be solved perfectly.
> [1] Optimize base64.b16decode to use compiled regex
> [1] https://bugs.python.org/issue35559
The simple solution to the perceived performance problem (not sure how
much of a problem it is in real life) is to have a stdlib function that
lazily-compiles a regex (*). Just like "re.compile", but lazy: you don't
bear the cost of compiling when simply importing the module, but once
the pattern is compiled, there is no overhead for looking up a global
cache dict.
No need for a dedicated literal.
(*) Let's call it "re.pattern", for example.
Regards
Antoine.
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