MySQL数据库连接

import pymysql
import contextlib


@contextlib.contextmanager
def get_cursor():
    """获取数据库光标"""
    db_settings = {
        'host': '',
        'user': '',
        'password': '',
        'database': '',
        'charset': 'utf8',
        'cursorclass': pymysql.cursors.DictCursor
    }
    try:
        conn = pymysql.connect(**db_settings)
        # 使用yield不但能够返回cursor
        # 而且cursor使用完毕后还会回到下一行继续执行
        # 这样数据库就能关闭！
        yield conn.cursor()
        conn.commit()
    except:
        conn.rollback()
        raise
    finally:
        conn.close()

 with db.get_cursor() as cursor:
            sql = ''
            cursor.execute(sql)
            rows = cursor.fetchall()
            ss = []
            for r in rows:
                s = Subject()
                for key in r:
                    setattr(s, key, r[key])
                ss.append(s)
            return ss