通过上下文管理器写一个mysql的连接，通过with管理

需求: 通过上下文管理器写一个mysql的连接，通过with管理

import pymysql


class MySQL:
    def __init__(self, *args, **kwargs):
        self.conn = pymysql.connect(*args, **kwargs)
        self.cursor = self.conn.cursor(cursor=pymysql.cursors.DictCursor)

    def __enter__(self):
        return self

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

        if exc_type:
            print(exc_type)
            print(exc_val)
            print(exc_tb)
        return True


with MySQL(
        host='127.0.0.1',
        port=3306,
        user='root',
        password='123',
        database='db1',
        charset='utf8',
        # autocommit=True
) as self:
    # 查
    '''
    sql = 'select username from user where password=123'
    affected_rows = self.cursor.execute(sql)

    print('affected_rows:', affected_rows)
    fetchall = self.cursor.fetchall()
    print(fetchall)     # [{'username': 'yang'}, {'username': 'egon'}]

    self.cursor.scroll(-2, 'relative')
    fetchone = self.cursor.fetchone()
    print(fetchone)     # {'username': 'yang'}

    # self.cursor.scroll(-1)
    self.cursor.scroll(0, 'absolute')
    fetchmany = self.cursor.fetchmany(2)
    print(fetchmany)    # [{'username': 'yang'}, {'username': 'egon'}]
    '''

    # 增
    """
    user_info = [
        ('lqz', '222'),
        ('wxx', '333'),
    ]
    sql = 'insert into user(username, password) values(%s, %s)'
    try:
        affected_rows = self.cursor.executemany(sql, user_info)
        print('affected_rows:', affected_rows)

        self.conn.commit()  # 提交
    except Exception as e:
        print(e)
        self.conn.rollback()

    self.cursor.execute('select * from user')
    fetchall = self.cursor.fetchall()
    print(fetchall)
    '''
    [{'id': 1, 'username': 'yang', 'password': '123'}, 
    {'id': 2, 'username': 'egon', 'password': '123'}, 
    {'id': 17, 'username': 'lqz', 'password': '222'}, 
    {'id': 18, 'username': 'wxx', 'password': '333'}]
    '''
    """

    # 删
    """
    sql = 'delete from user where id=18'
    try:
        self.cursor.execute(sql)
        self.conn.commit()  # 提交
    except Exception as e:
        print(e)
        self.conn.rollback()

    self.cursor.execute('select * from user')
    fetchall = self.cursor.fetchall()
    print(fetchall)
    '''
    [{'id': 1, 'username': 'yang', 'password': '123'}, 
    {'id': 2, 'username': 'egon', 'password': '123'}, 
    {'id': 17, 'username': 'lqz', 'password': '222'}]
    '''
    """

    # 改
    """
    sql = 'update user set username="egonDSB" where id=2'
    try:
        self.cursor.execute(sql)
        self.conn.commit()  # 提交
    except Exception as e:
        print(e)
        self.conn.rollback()

    self.cursor.execute('select * from user')
    fetchall = self.cursor.fetchall()
    print(fetchall)
    '''
    [{'id': 1, 'username': 'yang', 'password': '123'}, 
    {'id': 2, 'username': 'egonDSB', 'password': '123'},
    {'id': 17, 'username': 'lqz', 'password': '222'}]
    '''
    """