TypeError: not all arguments converted during string formatting

import asyncio
import aiomysql
import string

keys=list(string.ascii_uppercase)[0:23]


async def test_example_executemany(loop):
    conn = await aiomysql.connect(host='127.0.0.1', port=3306,
                                       user='root', password='',
                                       db='mint_loan', loop=loop)
    cur = await conn.cursor()
    #val=tuple(['S']*23)
    async with conn.cursor() as cur:
        await cur.executemany("INSERT INTO ABC ("+','.join(keys)+")"+"values ("+','.join(tuple(['%s'] * len(keys)))+")",  ['AB']*23)
        await conn.commit()
    conn.close()


loop = asyncio.get_event_loop()
loop.run_until_complete(test_example_executemany(loop))