Python-Django Caching images

Question

So i have read the Django-Docs about caching and understood i can cache data per view which is what i want to do. I have a URL like this : www.mysite.com/related_images/{image_id}. which calculates related images for the selected {image_id} and saves them to the disk so they can be accessed by the template. Thing is i don't want those images to stay there forever, but right now my view saves them to the disk without any caching, how can i make sure that by caching the view for a certain period of time, any files created by the view will be deleted when the cache expires ?.

Or if you have a better solution for my problem, I'm open for ideas. Is there a way to inject images from cache into templates without saving them on disk and providing a path for the html explicitly ?

here's a simplified version of the view:

def related_image(request, pk):

    original = get_object_or_404(Image, pk=pk)
    images = original.get_previous_views()
    for im in images:
        path = '/some/dir/'+str(im.id)+'.jpg'
        calculated_image = calculate(im,original)
        file = open(path)
        file.write(calculated_image)
        im.file_path = path

    return render_to_response('app/related_image.html', {'images': images})

Thanks :)

Answer 1

One solution would be to look at the file metadata for it's last modified date and compare that to a set expiration period.

For example:

import os

expiration_seconds = 3600
last_modified_time = os.path.getmtime(file_path)  # i.e. 1223995325.0
# that returns a float with the time of last modification since epoch, 
# so there's some logic to do to determine time passed since then.

if time_since_last_modified >= expiration_seconds:
    # delete the file
    os.remove(file_path)
    # then do your logic to get the file again