On 31.12.2018 12:23, Antoine Pitrou wrote:
On Thu, 27 Dec 2018 19:48:40 +0800 Ma Lin
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.
No need for a new function :-) We already have re.search() and re.match() which deal with compilation on-the-fly and caching. Perhaps the documentation should hint at this more explicitly... https://docs.python.org/3.7/library/re.html -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Experts (#1, Dec 31 2018)
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