views.py

def _document_last_modified(request, document_slug, document_locale):
    """Utility function to derive the last modified timestamp of a document.
    Mainly for the @condition decorator."""
    nk = u'/'.join((document_locale, document_slug))
    nk_hash = hashlib.md5(nk.encode('utf8')).hexdigest()
    cache_key = DOCUMENT_LAST_MODIFIED_CACHE_KEY_TMPL % nk_hash
    try:
        last_mod = cache.get(cache_key)
        if not last_mod:
            doc = Document.objects.get(locale=document_locale,
                                       slug=document_slug)

            # Convert python datetime to Unix epoch seconds. This is more
            # easily digested by the cache, and is more compatible with other
            # services that might spy on Kuma's cache entries (eg. KumaScript)
            last_mod = doc.modified.strftime('%s')
            cache.set(cache_key, last_mod)

        # Convert the cached Unix epoch seconds back to Python datetime
        return datetime.fromtimestamp(float(last_mod))

    except Document.DoesNotExist:
        return None