python
缘由
最近在折腾一个小东西需要抓取网上的页面,然后进行解析,将结果放到数据库中。了解到Python在这方面有优势,便选用之。因为我有台服务器上面安装有mysql,自然使用之。在进行数据库的这个操作过程中遇到了不少问题,这里记录一下,大家共勉。
python中mysql的调用
百度之后可以通过MySQLdb进行数据库操作,查看文档,了解到python中提供了一个_mysql时直接实现了mysql的c语言API。MySQLdb是对其在更高一层的封装,因此,使用起来更加方便。我们可以使用_mysql,但更好的方法是使用MySQLdb
安装中遇到的问题
在这个页面http://sourceforge.net/projects/mysql-python/可以下载到最新版本的MySQLdb,解压后执行安装时,可能会有一些问题。
-
通过
python setup.py build
执行安装会提示No module named setuptools
解决方法,安装之sudo apt-get install python-setuptools
-
再次执行,可能还是会出错 mysql_config not found
此时我们需要安装mysqld-dev
sudo apt-get install libmysqld-dev
- 可能再次执行还会出现错误,类似这样 `
building ‘mysql’ extension gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -Dversion_info=(1,2,3,’final’,0) -Dversion=1.2.3 -I/usr/include/mysql -I/usr/include/python2.7 -c mysql.c -o build/temp.linux-i686-2.7/mysql.o -DBIG_JOINS=1 -fno-strict-aliasing -DUNIV_LINUX -DUNIV_LINUX In file included from mysql.c:29:0: pymemcompat.h:10:20: fatal error: Python.h: No such file or directory
解决方案
sudo apt-get install python-dev
这步骤是安装python的一些开发用的头文件。
- 基本上前面三种之后,不会再出现其他问题了。但是如果mysql是自己安装的,并且lib文件没有放到/usr/local/lib下面则还会报错。
解决办法将文件软连接到这个目录下,或者修改系统的/etc/ld.so.cnf文件,把我们lib所在的目录放进去。两种方法都可以,然后在ldconfig,让其生效即可。
比如我们用第一种方法ln -s /usr/local/mysql/lib/mysql/libmysqlclient* /usr/lib
实际使用
-
引入MySQLdb库
import MySQLdb
-
连接数据库
conn=MySQLdb.connect(host=“localhost”,user=“root”,passwd=“sa”,db=“mytable”,charset=“utf8”)
提供的connect方法用来和数据库建立连接,接收数个参数,返回连接对象. -
执行语句和取结果
cursor=conn.cursor()
n=cursor.execute(sql,param)
首先,我们用使用连接对象获得一个cursor对象,接下来,我们会使用cursor提供的方法来进行工作.这些方法包括两大类:1.执行命令,2.接收返回值
后面再详细说,这里不详说 -
结束,关闭数据库连接
需要分别的关闭指针对象和连接对象.他们有名字相同的方法
cursor.close() conn.close()
常用操作API
对事务操作的支持,标准的方法 commit() 提交
rollback() 回滚
cursor用来执行命令的方法:
callproc(self, procname, args):用来执行存储过程,接收的参数为存储过程名和参数列表,返回值为受影响的行数
execute(self, query, args):执行单条sql语句,接收的参数为sql语句本身和使用的参数列表,返回值为受影响的行数
executemany(self, query, args):执行单挑sql语句,但是重复执行参数列表里的参数,返回值为受影响的行数 nextset(self):移动到下一个结果集
cursor用来接收返回值的方法:
fetchall(self):接收全部的返回结果行.
fetchmany(self, size=None):接收size条返回结果行.如果size的值大于返回的结果行的数量,则会返回cursor.arraysize条数据.
fetchone(self):返回一条结果行.
scroll(self, value, mode=‘relative’):移动指针到某一行.如果mode=‘relative’,则表示从当前所在行移动value条,如果 mode=‘absolute’,则表示从结果集的第一行移动value条.
最后插一句
电脑升级到ubuntu14.04重新装的,之前的博客仓库没了,重新从github上面拉回来,中间出了点差错,我删除文件,这篇文章差点没有了,不过还好现在能看到这篇文章。哈哈~~
原文地址:http://blog.isming.me/blog/2014/04/27/use-mysql-in-python/,欢迎转载,转载请注明出处!

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL is suitable for small and large enterprises. 1) Small businesses can use MySQL for basic data management, such as storing customer information. 2) Large enterprises can use MySQL to process massive data and complex business logic to optimize query performance and transaction processing.

InnoDB effectively prevents phantom reading through Next-KeyLocking mechanism. 1) Next-KeyLocking combines row lock and gap lock to lock records and their gaps to prevent new records from being inserted. 2) In practical applications, by optimizing query and adjusting isolation levels, lock competition can be reduced and concurrency performance can be improved.

MySQL is not a programming language, but its query language SQL has the characteristics of a programming language: 1. SQL supports conditional judgment, loops and variable operations; 2. Through stored procedures, triggers and functions, users can perform complex logical operations in the database.

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.


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