面向对象之魔术方法

# !/usr/bin/env python3
# -*- coding: utf-8 -*-
# @Time : 2020/5/19 22:00
# @Author : "小多肉"
# @Email : 1021181701@qq.com
# @File : 面向对象之魔术方法.py
# @Software: PyCharm

"""TODO:
第一题：基于pymysql模块实现一个数据库操作的上下文管理器（目的：实现自动关闭连接对象和游标）

第二题：自定义一个列表类型，实现对象可以之间可以 使用 -  来进行操作
# 要求：如果一个对象减去另一个对象，则把和被减对象中一样的数据给删除掉
# 如下：
li1 = MyList([11, 22, 33, 44])
li2 = MyList([1, 22, ])
res = li1 - li2
# res 打印的结果为[11,33,44]
"""
import pymysql


class DBContext:

    def __init__(self,
                 host=None,
                 port=3306,
                 user='root',
                 password='',
                 charset='utf8',
                 database=None,
                 **kwargs
                 ):
        self.conn = pymysql.connect(host=host,
                                    port=port,
                                    user=user,
                                    password=password,
                                    charset=charset,
                                    database=database,
                                    **kwargs
                                    )

        self.cursor = self.conn.cursor()

    def __enter__(self):

        return self.conn, self.cursor

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.cursor.close()
        self.conn.close()


class ListSub:

    def __init__(self,li:list):
        self.li = li

    def __sub__(self, other):
        for i in other.li:
            if i in self.li:
                self.li.remove(i)
        return self.li

    def __add__(self, other):
        return self.li + other.li


if __name__ == '__main__':
    print("----------------------第一题------------------------")
    with DBContext(host="192.168.5.20",password="love520",database="love") as (my_conn,my_cursor):
        sql = "select to_date('2020-12-01' ,'YYYY-MM-DD') - to_date('2020-05-20','YYYY-MM-DD') from dual;"
        my_cursor.execute(sql)
        my_conn.commit()
        data = my_cursor.fetchone()
        print(data)

    print("----------------------第二题------------------------")
    li1 = ListSub([11, 22, 33, 44])
    li2 = ListSub([1, 22, ])
    res = li1 - li2
    print(res)
    res2 = li1 + li2
    print(res2)