python3 操作MYSQL实例及异常信息处理--用traceback模块

# 用traceback模块查看异常
import traceback 
import pymysql

db = pymysql.connect(host='localhost', user='root', password='root', port=3306, db='spiders')
cursor = db.cursor()

try:  
    sql = 'SELECT graph, brand_name FROM base_info'
    # 执行sql语句  
    cursor.execute(sql)  
    result = cursor.fetchone()  
except: 
    # 输出异常信息  
    traceback.print_exc()  
    # 如果发生异常，则回滚  
    db.rollback()  
finally:  
    # 最终关闭数据库连接  
    db.close()