File cache for images

[Дамјан Георгиев�ки]

I'm looking for a way to cache some modified images as files (in a python
program ofcourse). The scenario would look like this:

getmodifiedimage(filename):
is it in cache?
is the cache up to date (not older than file)
if not, modify filename and store in cache (keyed by filename +
modification)
return modified image
I'm looking for prior-art before inventing it myself :)

--
дамјан

If Bill Gates had a dime for every time a Windows box crashed...
...Oh, wait a minute, he already does.

[Fredrik Lundh]

"[e-mail]" wrote:

I'm looking for a way to cache some modified images as files (in a python
program ofcourse). The scenario would look like this:

getmodifiedimage(filename):
is it in cache?
is the cache up to date (not older than file)
if not, modify filename and store in cache
(keyed by filename + modification)
return modified image

I'm looking for prior-art before inventing it myself :)

I'm not sure what "modify filename" means, but a straightforward
solution is not that much longer than your pseudocode:

def getmodifiedimage(filename, cache={}):
try:
image, mtime = cache[filename]
if mtime < os.path.getmtime(filename):
raise KeyError
except KeyError:
image = open(filename, "rb").read() # or something
cache[filename] = image, os.path.getmtime(filename)
return image

</F>

[Дамјан Георгиев�ки]

> I'm looking for a way to cache some modified images as files (in a python

program ofcourse). The scenario would look like this:

getmodifiedimage(filename):
is it in cache?
is the cache up to date (not older than file)
if not, modify filename and store in cache (keyed by filename +
modification)
return modified image
I'm looking for prior-art before inventing it myself :)

I've read Fredrik Lundh answer on Google Groups, since it didn't appear on
my news server.

I'm not sure what "modify filename" means

I dont want to cache file in memory (a dict in your ex.), access to the file
is cheap. I want to modify the image (say create a thumbnail, or watermark
it) and cache the thumbnail in a file.

.... but anyway it should be easy to implement really... It's just I've had a
fealing I miss something... well maybe I miss the implementation of
removing least recently used files in the cache, when the cache becomes
full (as configured).

--
дамјан

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