SVFS is a simple virtual filesystem for Python.
SVFS allows to create virtual filesystem inside file on real filesystem.
It can be used to store multiple files inside single file (with directory structure).
Unlike archives, SVFS allows to modify files in-place.
SVFS files use file-like interface, so they can be used (pretty much) like regular Python file objects.
Finally, it's implemented in pure python and doesn't use any 3rd party modules, so it should be very portable.
Tests show write speed to be around 10-12 MB/s and read speed to be around 26-28 MB/s.