Re: Compiling regex inside function?

[Anthra Norell]

alex23 wrote:

Anthra Norell <anthra.nor...@bluewin.ch> wrote:

def entries (l):
        r = re.compile ('([0-9]+) entr(y|ies)')
        match = r.search (l)
        if match: return match.group (1)

So the question is: does "r" get regex-compiled once at py-compile time
or repeatedly at entries() run time?

The docs say:
The compiled versions of the most recent patterns passed to re.match
(), re.search() or re.compile() are cached, so programs that use only
a few regular expressions at a time needn’t worry about compiling
regular expressions.

(But they don't say how few is 'only a few'...)

If you're concerned about it, you could always set the compiled
pattern to a default value in the function's argspec, as that _is_
only executed the once:

def entries(line, regex = re.compile('([0-9]+) entr(y|ies)'):
    match = regex.search(line)
    ...

Excellent idea! Thank you all for the tips.

Frederic

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