# Map spreadsheet manipulation

def merge_rows(*rows):

    '''e.g. ['a','b'] + ['','y','z'] = ['a','b; y','z']'''

    def get(row, i):

        try: return row[i]

        except IndexError: return ''

    return ['; '.join(filter(lambda v: v != '', [get(row, i) for row in rows]))

    for i in xrange(max(map(len, rows)))]