Python编程：利用上下文管理器管理MySQL的链接对象

# -*- coding: utf-8 -*-
import MySQLdb
class DataBase(object):
    def __init__(self, hostname, username, password, database, port, charset='utf-8'):
        self.conn = MySQLdb.Connect(
            host=hostname,
            user=username,
            passwd=password,
            db=database,
            port=port,
            charset=charset,
            autocommit=True
        )
        self.cursor = self.conn.cursor()
    def __enter__(self):
        return self.cursor
    def __exit__(self, exc_type, exc_val, exc_tb):
        self.cursor.close()
        self.conn.close()

exc_type : Type 异常类型
exc_val : Value 异常值
exc_tb : TreacBack 异常回溯追踪