Python通过DOM和SAX方式解析XML的应用实例分享
XML.DOM
需求
有一个表，里面数据量比较大，每天一更新，其字段可以通过xml配置文件进行配置，即，可能每次建表的字段不一样。
上游跑时会根据配置从源文件中提取，到入库这一步需要根据配置进行建表。
解决
写了一个简单的xml，配置需要字段及类型
上游读取到对应的数据
入库这一步，先把原表删除，根据配置建新表
XML文件
<?xml version="1.0" encoding="UTF-8"?> <!-- 表名 ,数据库名 可灵活配置插入哪个库哪个表 --> <table name="top_query" db_name="evaluting_sys"> <!-- 非业务主键，自增长,可配名，其他 INTEGER UNSIGNED AUTO_INCREMENT --> <primary_key> <name>id</name> </primary_key> <!-- 字段开始 --> <field> <name>query</name> <type>varchar(200)</type> <is_index>false</is_index> <description>query</description> </field> <field> <name>pv</name> <type>integer</type> <is_index>false</is_index> <description>pv</description> </field> <field> <name>avg_money</name> <type>integer</type> <is_index>false</is_index> <description></description> </field> <!-- 字段配置结束 --> </table>
处理脚本
#!/usr/bin/python
# -*- coding:utf-8 -*-
#author: wklken
#desc: use to read db xml config.
#-----------------------
#2012-02-18 created
#----------------------
import sys,os
from xml.dom import minidom, Node
def read_dbconfig_xml(xml_file_path):
content = {}
root = minidom.parse(xml_file_path)
table = root.getElementsByTagName("table")[0]
#read dbname and table name.
table_name = table.getAttribute("name")
db_name = table.getAttribute("db_name")
if len(table_name) > 0 and len(db_name) > 0:
db_sql = "create database if not exists `" + db_name +"`; use " + db_name + ";"
table_drop_sql = "drop " + table_name + " if exists " + table_name + ";"
content.update({"db_sql" : db_sql})
content.update({"table_sql" : table_drop_sql })
else:
print "Error:attribute is not define well! db_name=" + db_name + " ;table_name=" + table_name
sys.exit(1)
#print table_name, db_name
table_create_sql = "create table " + table_name +"("
#read primary cell
primary_key = table.getElementsByTagName("primary_key")[0]
primary_key_name = primary_key.getElementsByTagName("name")[0].childNodes[0].nodeValue
table_create_sql += primary_key_name + " INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,"
#print primary_key.toxml()
#read ordernary field
fields = table.getElementsByTagName("field")
f_index = 0
for field in fields:
f_index += 1
name = field.getElementsByTagName("name")[0].childNodes[0].nodeValue
type = field.getElementsByTagName("type")[0].childNodes[0].nodeValue
table_create_sql += name + " " + type
if f_index != len(fields):
table_create_sql += ","
is_index = field.getElementsByTagName("is_index")[0].childNodes[0].nodeValue
table_create_sql += ");"
content.update({"table_create_sql" : table_create_sql})
#character set latin1 collate latin1_danish_ci;
print content
if __name__ == "__main__":
read_dbconfig_xml(sys.argv[1])
涉及方法
root = minidom.parse(xml_file_path) 获取dom对象
root.getElementsByTagName("table") 根据tag获取节点列表
table.getAttribute("name") 获取属性
primary_key.getElementsByTagName("name")[0].childNodes[0].nodeValue 获取子节点的值（id 得到id）
SAX
需求
读取xml数据文件，文件较大，需要实时处理插入到数据库
xml文档
<PERSONS> <person> <id>100000</id> <sex>男</sex> <address>北京，海淀区</address> <fansNum>437</fansNum> <summary>1989</summary> <wbNum>333</wbNum> <gzNum>242</gzNum> <blog>null</blog> <edu>大学</edu> <work></work> <renZh>1</renZh> <brithday>2月14日</brithday> </person> </PERSONS>
处理
sax处理时并不会像dom一样可以以类似节点的维度进行读取,它只有 开始标签 内容 结束标签 之分
处理思想是：通过一个handler，对开始标签，内容，结束标签各有一个处理函数
代码及注解
person 处理类
from xml.sax import handler,parseString
class PersonHandler(handler.ContentHandler):
def __init__(self, db_ops):
#db op obj
self.db_ops = db_ops
#存储一个person的map
self.person = {}
#当前的tag
self.current_tag = ""
#是否是tag之间的内容 ，目的拿到tag间内容，不受空白的干扰
self.in_quote = 0
#开始，清空map
def startElement(self, name, attr):
#以person，清空map
if name == "person":
self.person = {}
#记录 状态
self.current_tag = name
self.in_quote = 1
#结束，插入数据库
def endElement(self, name):
#以person结尾 代表读取一个person的信息结束
if name == "person":
#do something
in_fields = tuple([ ('"' + self.person.get(i,"") + '"') for i in fields ])
print in_sql % in_fields
db_ops.insert( in_sql%(in_fields))
#处理
self.in_quote = 0
def characters(self, content):
#若是在tag之间的内容，更新到map中
if self.in_quote:
self.person.update({self.current_tag: content})
加上入库的完整代码
#!/usr/bin/python
# -*- coding:utf-8 -*-
#parse_person.py
#version : 0.1
#author : wukunliang@163.com
#desc : parse person.xml and out sql
import sys,os
import MySQLdb
reload(sys)
sys.setdefaultencoding('utf-8')
in_sql = "insert into person(id,sex,address,fansNum,summary,wbNum,gzNum,blog,edu,work,renZh,brithday) values(%s, %s, %s, %s, %s, %s,
%s, %s, %s, %s, %s, %s)"
fields = ("id","sex","address","fansNum","summary","wbNum","gzNum","blog","edu","work","renZh","brithday")
#数据库方法
class Db_Connect:
def __init__(self, db_host, user, pwd, db_name, charset="utf8", use_unicode = True):
print "init begin"
print db_host, user, pwd, db_name, charset , use_unicode
self.conn = MySQLdb.Connection(db_host, user, pwd, db_name, charset=charset , use_unicode=use_unicode)
print "init end"
def insert(self, sql):
try:
n = self.conn.cursor().execute(sql)
return n
except MySQLdb.Warning, e:
print "Error: execute sql '",sql,"' failed"
def close(self):
self.conn.close()
#person 处理类
from xml.sax import handler,parseString
class PersonHandler(handler.ContentHandler):
def __init__(self, db_ops):
#db op obj
self.db_ops = db_ops
#存储一个person的map
self.person = {}
#当前的tag
self.current_tag = ""
#是否是tag之间的内容
self.in_quote = 0
#开始，清空map
def startElement(self, name, attr):
#以person，清空map
if name == "person":
self.person = {}
#记录 状态
self.current_tag = name
self.in_quote = 1
#结束，插入数据库
def endElement(self, name):
#以person结尾 代表读取一个person的信息结束
if name == "person":
#do something
in_fields = tuple([ ('"' + self.person.get(i,"") + '"') for i in fields ])
print in_sql % in_fields
db_ops.insert( in_sql%(in_fields))
#处理
self.in_quote = 0
def characters(self, content):
#若是在tag之间的内容，更新到map中
if self.in_quote:
self.person.update({self.current_tag: content})
if __name__ == "__main__":
f = open("./person.xml")
#如果源文件gbk 转码 若是utf-8，去掉decode.encode
db_ops = Db_Connect("127.0.0.1", "root", "root", "test")
parseString(f.read().decode("gbk").encode("utf-8"), PersonHandler(db_ops))
f.close()
db_ops.close()
平时拿python来分析数据，工具脚本还有hadoop streamming，但是用的面和深度实在欠缺 只能说道行还浅，需要多多实践
