When to compile regex?

[Fredrik Lundh]

Tim Ottinger <tottinge at concentric.net> wrote:
> >In section 4.2.3 of the Python Library Reference (1.5.2) it says that
> >using compile is more efficient "when the expresion will be used several
> >times in a single program". I'm trying to figure out the intended
> >meaning of this. Does that mean "executed more than once", or "occurs
> >more than once in the program text"? Specifically, if it only occurs
> >once, but that is in a loop, is there an advantage to compiling before
> >entering the loop?
>
> It has to be compiled before it's used. If you don't compile it, then
> it will be compiled at the point of use, as a temporary, and then
> tossed away later.

better make that:

    ...compiled at the point of use, stored in a cache,
    possibly tossed away later, if the cache fills up.

in 1.5.2, the cache holds 20 regular expressions.  in 1.6,
it will probably be much larger.

</F>