When processing a file, how do I obtain the current line number?

Question

When I am looping over a file using the construct below, I also want the current line number.

    with codecs.open(filename, 'rb', 'utf8' ) as f:
        retval = []
        for line in f:
            process(line)

Does something akin to this exist ?

    for line, lineno in f: