Python系列之入门篇——MYSQL

Python系列之入门篇——MYSQL

简介

python提供了两种mysql api, 一是MySQL-python(不支持python3),二是PyMYSQL(支持python2和python3)

代码示例

1. 安装

   pip install MySQL-python
   

2. 引入相关模块

   import MySQLdb
   

3. 创建客户端

   conn = MySQLdb.connect(host, user, passwd, database, charset='utf8')
   cur = conn.cursor()
   

4. 插入

   """
   it has two methods to insert, one is execute() one by one, and another is executemany() multi-row, it has same principle, both execute one by one
   data : [()]
   affects : int   affect rownums
   """
   sql = 'INSERT INTO student(no, name, sex, age) VALUES(%s, %s, %s, %s)'
   data = [(001, 'john', 'male', '20'), (002, 'merry', 'female', '19')]
   affects = cur.execute(sql, data)
   conn.commit()
   

5. 查询

   """
   fetchone() : get only one row
   fetchmany(size=100) : get some rows as you set the size
   fetchall() : get all rows
   """
   sql = 'SELECT no, name, sex, age FROM student'
   cur.execute(sql)
   conn.commit()
   rows = cur.fetchall()
   

6. 异常处理

ERROR 2006 (HY000): MySQL server has gone away

异常描述: 见 http://www.cnblogs.com/dzqk/p/8237030.html

解决方案: 在有大数据量分析的时候,执行sql前判断连接的状态,请看下面的连接重试方法

def conn_retry(logger, conn, retry_count, *args):
    """
    Mysql reconnect

    Parameters
    ----------
    logger : Logger
    conn : Connection
    retry_count : int
    args : tuple --> host, user, passwd, database

    Returns
    -------
    conn : Connection
    """
    try:
        conn.ping(True)
        return conn
    except Exception as e:
        logger.error(e)
        logger.error('Mysql connection is closed, Now retry connect...')
        retry = 0
        while retry < retry_count:
            try:
                logger.debug('Retry times is %i' % (retry + 1))
                return MySQLdb.connect(list(args)[0], list(args)[1], list(args)[2], list(args)[3], charset='utf8')
            except Exception as e:
                logger.error(repr(e))
                retry += 1
        else:
            return None