sqlalchemy写好数据库类，在mysql创建表问题，大佬们

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写了一个继承 declarative_base()的Base类，还有继承Base类的BaseModel类，同步数据库想让自动创建表，但是总是不能，问题出在哪里？

from sqlalchemy import create_engine, MetaData
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('mysql+pymysql://root:123456@localhost:3306/Spider', echo=True)
Base = declarative_base()


class BaseModel(Base):
    __abstract__ = True
    __metadata__ = MetaData(bind=engine)
    __table_arhs__ = {
        'mysql_engine': 'InnoDb',
        'mysql_charset': 'utf8'
    }

if __name__ == '__main__':
    BaseModel.__metadata__.create_all()

其中一个表model类如下：

from sqlalchemy import Column
from sqlalchemy.dialects.mysql import INTEGER, VARCHAR

from common.db import BaseModel


class CityModel(BaseModel):
    __tablename__ = 'city'

    id = Column(INTEGER, primary_key=True)
    name = Column(VARCHAR(64))

打印出来的数据库命令信息如下

2017-09-08 22:24:15,737 INFO sqlalchemy.engine.base.Engine SHOW VARIABLES LIKE 'sql_mode'
2017-09-08 22:24:15,737 INFO sqlalchemy.engine.base.Engine {}
2017-09-08 22:24:15,750 INFO sqlalchemy.engine.base.Engine SELECT DATABASE()
2017-09-08 22:24:15,750 INFO sqlalchemy.engine.base.Engine {}
2017-09-08 22:24:15,751 INFO sqlalchemy.engine.base.Engine show collation where `Charset` = 'utf8' and `Collation` = 'utf8_bin'
2017-09-08 22:24:15,752 INFO sqlalchemy.engine.base.Engine {}
2017-09-08 22:24:15,753 INFO sqlalchemy.engine.base.Engine SELECT CAST('test plain returns' AS CHAR(60)) AS anon_1
2017-09-08 22:24:15,754 INFO sqlalchemy.engine.base.Engine {}
2017-09-08 22:24:15,754 INFO sqlalchemy.engine.base.Engine SELECT CAST('test unicode returns' AS CHAR(60)) AS anon_1
2017-09-08 22:24:15,754 INFO sqlalchemy.engine.base.Engine {}
2017-09-08 22:24:15,755 INFO sqlalchemy.engine.base.Engine SELECT CAST('test collated returns' AS CHAR CHARACTER SET utf8) COLLATE utf8_bin AS anon_1
2017-09-08 22:24:15,755 INFO sqlalchemy.engine.base.Engine {}

到底是那里的问题。。。