• sqlalchemy根据表名动态创建model类


    作用如题,直接上代码吧,另外还支持 copy一张表的表结构,新建表并获得model对象
    
    # coding: utf-8
    import traceback
    
    from sqlalchemy import (BigInteger, Column, DateTime, Integer, MetaData,
                            String, Table, create_engine, text)
    from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy.orm import mapper
    from sqlalchemy.schema import CreateTable
    
    
    # 本地数据库
    engineLocal = create_engine('mysql+pymysql://root:root@127.0.0.1:3306/lingyun?charset=utf8')
    
    
    Base = declarative_base()
    metadata = MetaData()
    
    def dictToObj(results, to_class):
        """将字典list或者字典转化为指定类的对象list或指定类的对象
        python 支持动态给对象添加属性,所以字典中存在而该类不存在的会直接添加到对应对象
        """
        if isinstance(results, list):
            objL = []
            for result in results:
                obj = to_class()
                for r in result.keys():
                    obj.__setattr__(r, result[r])
                objL.append(obj)
            return objL
        else:
            try:
                obj = to_class()
                for r in results.keys():
                    obj.__setattr__(r, results[r])
                return obj
            except Exception as e:
                print(e)
                traceback.print_exc()
                return None
        # else:
        #     print("传入对象非字典或者list")
        #     return None
    
    def getModel(name, engine):
        """根据name创建并return一个新的model类
        name:数据库表名
        engine:create_engine返回的对象,指定要操作的数据库连接,from sqlalchemy import create_engine
        """
        Base.metadata.reflect(engine)
        table = Base.metadata.tables[name]
        t = type(name,(object,),dict())
        mapper(t, table)
        Base.metadata.clear()
        return t
    
    def createTableFromTable(name, tableNam, engine):
        """copy一个已有表的结构,并创建新的表
        """
        metadata = MetaData(engine)
        Base.metadata.reflect(engine)
        # 获取原表对象
        table = Base.metadata.tables[tableNam]
        # 获取原表建表语句
        c = str(CreateTable(table))
        # 替换表名
        c = c.replace("CREATE TABLE " + tableNam, "CREATE TABLE if not exists " + name)
        db_conn = engine.connect()
        db_conn.execute(c)
        db_conn.close()
        Base.metadata.clear()
    
    def getNewModel(name, tableNam, engine):
        """copy一个表的表结构并创建新的名为name的表并返回model类
        name:数据库表名
        tableNam:copy的表表名
        engine:create_engine返回的对象,指定要操作的数据库连接,from sqlalchemy import create_engine
        """
        createTableFromTable(name, tableNam, engine)
        return getModel(name, engine)
    

     https://blog.csdn.net/j_object/article/details/80118657 

  • 相关阅读:
    阿里P8聊并发编程:线程中断和终止
    浅谈Java中的锁:Synchronized、重入锁、读写锁
    史上最全Java面试题!进程,线程相关部分下篇(带全部答案)
    @史上最全Java面试题!关于volatile关键字篇(带全部答案)
    @史上最全Java面试题!进程,线程相关部分上篇(带全部答案)
    一道号称“史上最难”java面试题引发的线程安全思考,掌握了吗?
    stopWatch
    mysql语句及执行计划
    Awr
    文件下载
  • 原文地址:https://www.cnblogs.com/hedianzhan/p/9639563.html
Copyright © 2020-2023  润新知