This python library can parse the ISO 9660 disk image format including Rock Ridge extensions. It can load ISOs from the local filesystem or via HTTP, and will only read and cache sectors as necessary. You list directory contents, extract files, and retrieve metadata.
This package is unmaintained. The author now maintains the pathlab package, which includes support for ISO 9660 and Rock Ridge. The pycdlib package may also be of interest if you need Joliet / UDF support.
$ pip install isoparserimport isoparser
iso = isoparser.parse("http://www.microsoft.com/linux.iso")
print iso.record("boot", "grub").children
print iso.record("boot", "grub", "grub.cfg").content