kj wrote:
In <mailman.120.1253406305.2807.python-l...@python.org> Robert Kern
<robert.k...@gmail.com> writes:
kj wrote:
My Python code is filled with assignments of regexp objects to
globals variables at the top level; e.g.:
_spam_re = re.compile('^(?:ham|eggs)$', re.I)
Don't like it. My Perl-pickled brain wishes that re.compile was
a memoizing method, so that I could use it anywhere, even inside
tight loops, without ever having to worry about the overhead of
regexp compilation.
Just use re.search(), etc. They already memoize the compiled regex objects.
Thanks.
I find the docs are pretty confusing on this point. They first
make the point of noting that pre-compiling regular expressions is
more efficient, and then *immediately* shoot down this point by
saying that one need not worry about pre-compiling in most cases.
From the docs:
...using compile() and saving the resulting regular expression
object for reuse is more efficient when the expression will be
used several times in a single program.
Note: 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.
Honestly I don't know what to make of this... I would love to see
an example in which re.compile was unequivocally preferable, to
really understand what the docs are saying here...
kynn
Looking in the code for re in 2.5:
.
.
.
_MAXCACHE = 100
.
.
.
if len(_cache) >= _MAXCACHE:
_cache.clear()
.
.
.
so when you fill up, you lose the entire cache. On the other hand, I (a
re novice, to be sure) have only used between two to five in any one
program... it'll be a while before I hit _MAXCACHE!
~Ethan~
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