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  • MySQL--07(pymysql)

    pymysql

    安装pymysql

    pip install pymysql

    使用 pymysql

    import pymysql
    
    from  functools import  wraps
    
    # 四个参数(连接地址,登录数据库用户,数据连接密码,数据库名字)
    db = pymysql.connect('localhost', 'root', 'mysql', 'books')
    
    c = db.cursor()  # 获取游标cursor
    
    ## 查询所有表
    sql = 'show tables;'
    c.execute(sql)  # 执行sql语句
    query = c.fetchall()
    # fetch 取,获取  all 全部
    
    # print(query)
    
    ## 查询books表里的所有记录
    sql = 'select * from books'
    c.execute(sql)
    query = c.fetchall()
    # print(query)
    
    # CURD
    
    # sql = '''
    # insert into books(book_name,author,publish,prints,publish_date)values
    # ('三国演义','罗贯中','中州古籍出版社',100,'2019-04-01');
    # '''
    # c.execute(sql)
    # db.commit()  # 提交
    # query=c.fetchall()
    # print(query)
    
    
    sql = 'select * from books'
    c.execute(sql)
    query = c.fetchall()
    
    
    # print(query)
    
    # # pymysql 删除数据
    # sql ='delete from books where id=4'
    # try:
    #     c.execute(sql)
    #     db.commit()  # 只要涉及到数据变更的,一定要带上 commit
    # except:
    #     db.rollback()
    #
    
    # pymysql 修改数据
    # sql='update books set author="四毛" where id=1'
    #
    # try:
    #     c.execute(sql)
    #     db.commit()
    # except:
    #     db.rollback()
    
    # sql='select * from books'
    # # [{},{},{}]
    # try:
    #     c.execute(sql)
    #     query =c.fetchall()
    #     res =[]
    #     for x in query:
    #         temp ={}
    #         temp['book_name']=x[1]
    #         temp['author']=x[2]
    #         res.append(temp)
    # except:
    #     print('查询错误')
    #
    # print(res)
    
    # c.close()
    # db.close()
    
    
    '''
    定义单例装饰器
    '''
    def singleton(cls):
        _instance ={}  # 定义集合放置cls的实例
        @wraps(cls)
        def getInstance(*args,**kwargs):
            if cls not in _instance:  # 如果没有实例,则生成一个
                _instance[cls]=cls(*args,**kwargs)
            return _instance[cls]   # 返回实例
        return  getInstance
    
    
    @singleton
    class pysql(object):
    
        def __init__(self):
            print('class instance1')
    
    
    p1 = pysql()
    p2 = pysql()
    print(id(p1))
    print(id(p2))
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  • 原文地址:https://www.cnblogs.com/xinzaiyuan/p/13501889.html
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