orm的作用

听说可以不用写sql语句就可以实现对数据库的操作(当然这也是orm的作用),于是就有了这篇文章...

下面是简单的代码

from pymysql import connect


class Field(object):
    def __init__(self, args):
        self.args = args


class ChangeClass(type):
    def __new__(cls, class_name, super_name, attrs):
        print(attrs)
        sql_dict = dict()
        for key, value in attrs.items():
            if isinstance(value, Field):
                sql_dict[key] = value.args
        print(sql_dict)
        attrs['sql_dict'] = sql_dict
        attrs['table_name'] = class_name.lower()
        return type.__new__(cls, class_name, super_name, attrs)


class Table(object, metaclass=ChangeClass):

    # 把table设置为父类

    # # 让此字典自动生成
    # # sql_dict = {"id": "int unsigned", "name": "varchar(30)"}
    # # 这里是属性,写成键值的形式
    # table_name = "kaka"
    # # 写成元祖方便区别写入元素,方便查找
    # id = ("int unsigned",)
    # name = ("varchar(30)",)
    # # sql_dict = {"id": id, "name": name}

    def create_table(self):

        # 1 连接数据库
        # 2 操作数据库
        # 3 关闭

        # 连接数据库

        conn = connect(host='localhost', port=3306, database='zxc', user='root', password='mysql', charset='utf8')

        # 获取游标
        cs1 = conn.cursor()

        # 创建字典保存键值关系
        sql_list = list()
        # 获取字典内的值
        for key, values in self.sql_dict.items():
            sql_list.append("%s %s" % (key, values))
            # sql_list.append(key, values)

        # user(id int unsigned, name varchar(20))
        # 操作数据库
        sql = """ create table if not exists %s(%s) """ % (self.table_name, ",".join(sql_list))
        print(sql)
        cs1.execute(sql)

        # 提交！！！
        conn.commit()
        # 获取数据
        # data = cs1.fetchall()

        # 关闭
        cs1.close()
        conn.close()

    def insert(self, **kwargs):
        print(kwargs)
        # (2.创建列表,我们想要得到的值在调用函数时输入,此时分析一下,输入方式是键值对,所以用**kwargs,接下来就是取出对应的键与值了)
        list_key = list()
        list_value = list()
        # (3.把取出的值放进对应的列表里,这里要注意在数据库中的值都是以)
        for key, value in kwargs.items():
            list_key.append(key)
            list_value.append(""" '%s' """ % str(value))  #这里会出错sequence item 0: expected str instance, int found在另一篇文章会说
            #list_value.append(value)


        # 连接数据库
        conn = connect(host='localhost', port=3306, database='zxc', user='root', password='mysql', charset='utf8')
        # 获取游标
        cs1 = conn.cursor()
        # 操作数据库(1.清楚要获得什么类型的内容-->答案是列表!ok,我们去创建列表)
        sql = """insert into %s(%s) values(%s);""" % (self.table_name, ",".join(list_key), ",".join(list_value))
        print(sql)
        rows = cs1.execute(sql)

        # 提交！！！
        conn.commit()

        # 关闭
        cs1.close()
        conn.close()
# #################################框架################################################################

class Student(Table):
    name = Field('varchar(30)')
    num = Field('int')

# class User(Table):
#     name = ("varchar(30)",)
#     age = ("int",)


def main():
    student = Student()
    student.create_table()
    student.insert(name='zxc', num=22)


if __name__ == '__main__':
    main()