comple list slices

[johnzenger at gmail.com]

You don't need to copy the list; but if you don't, your original list
will be emptied.

Len(rows) recalculates each time the while loop begins.  Now that I
think of it, "rows != []" is faster than "len(rows) > 0."

By the way, you can also do this using (gasp) a control index:

def grouprows(rows):
    index = 0
    while len(rows) > index:
        rowspan = rows[index]["rowspan"]
        yield rows[index:rowspan + index]
        index += rowspan

...which kind of brings us back to where we started.