filecache 0.75

Persistent caching decorator

filecache

filecache is a decorator which saves the return value of functions even
after the interpreter dies. For example this is useful on functions that download
and parse webpages. All you need to do is specify how long
the return values should be cached (use seconds, like time.sleep).

USAGE:

from filecache import filecache

@filecache(24 * 60 * 60)
def time_consuming_function(args):
# etc

@filecache(filecache.YEAR)
def another_function(args):
# etc


NOTE: All arguments of the decorated function and the return value need to be
picklable for this to work.

NOTE: The cache isn't automatically cleaned, it is only overwritten. If your
function can receive many different arguments that rarely repeat, your
cache may forever grow. One day I might add a feature that once in every
100 calls scans the db for outdated stuff and erases.

NOTE: This is less useful on methods of a class because the instance (self)
is cached, and if the instance isn't the same, the cache isn't used. This
makes sense because class methods are affected by changes in whatever
is attached to self.

Tested on python 2.7 and 3.1

License: BSD, do what you wish with this. Could be awesome to hear if you found
it useful and/or you have suggestions. ubershmekel at gmail


A trick to invalidate a single value:

@filecache.filecache
def somefunc(x, y, z):
return x * y * z

del somefunc._db[filecache._args_key(somefunc, (1,2,3), {})]
# or just iterate of somefunc._db (it's a shelve, like a dict) to find the right key.