python-连接mysql查询数据

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一、安装组件

pymysql

# 执行在线安装命令
pip install pymysql

二、代码示例

import pymysql

class neo_mysql:
    def __init__(self):
        self.db_host = '127.0.0.1'
        self.db_user = 'root'
        self.db_passwd = '123456'
    
    # 查询sql
    # 参数含义
    # sql: 查询的sql语句
    # row: 取查询结果的第几行数据
    # col: 取行的第几列数据
    def query_mysql(self, sql, row=None, col=None):
        conn = pymysql.connect(host = self.db_host, user = self.db_user, passwd = self.db_passwd)
        cur = conn.cursor()
        cur.execute(sql)
        data = cur.fetchall()
        cur.close()
        conn.close()
        # 查询到有数据则进入行判断，row有值且值有效则取指定行数据，无值则默认第一行
        if data != None and len(data) > 0:
            if row != None:
                if row >= 0 and row < len(data):
                    value = data[row]
                    info = '查询第' + str(row) + '行数据'
                    print(info)
                else:
                    value = None
                    print("行取值超出范围！")
                    return None
            else:
                value = data[0]
                print("默认第一行...")
        else:
            value = None
            print("未查询到数据！")
            return None
        # 列判断，col有值且值有效则取指定列数据，无值则默认第一列
        if col != None:
            if col >= 0 and col < len(value):
                value = str(value[col])
                info = '查询第' + str(col) + '列数据'
                print(info)
            else:
                value = None
                print("列取值超出范围！")
                return None
        else:
            value = str(value[0])
            print("默认第一列...")
        return value

if __name__ == "__main__":
    my_test = neo_mysql()
    sql = 'SELECT * FROM mysql.user;'
    result = my_test.query_mysql(sql, col=1)
    print("查询结果为", result)