cursor.execute('INSERT INTO media_files (%s) VALUES (%%s, %%s, %%s, %%s, ...)' % ','.join(fieldlist), valuelist)
Para deixar mais claro:
sql = 'INSERT INTO media_files (%s) VALUES (%%s, %%s, %%s, %%s, ...)' % ','.join(fieldlist)
cursor.execute(sql, valuelist)
