Example of using Python to parse XML through DOM and SAX

This article mainly introduces how to use Python to parse XML application instances through DOM and SAX. For the two parsing methods, Python has related modules available for use. For more information, see XML. DOM

Requirement
There is a table with a large amount of data, which is updated every day. Its fields can be configured through the xml configuration file, that is, the fields of each table may be different.

During the upstream running, the source file is extracted according to the configuration. to import the data to the database, you need to create a table based on the configuration.

Solution
A simple xml file is written, and fields and types are required for configuration.

Upstream reads the corresponding data

In this step, delete the original table and create a new table based on the configuration.

XML file

<? Xml version = "1.0" encoding = "UTF-8"?>
 
 
  
   
Id
  
 
 
  
   
Query
  
  
   
Varchar (200)
  
  
   
False
  
  
   
Query
  
 
 
  
   
Pv
  
  
   
Integer
  
  
   
False
  
  
   
Pv
  
 
 
  
   
Avg_money
  
  
   
Integer
  
  
   
False
  
  
 
 
 

Process scripts

#!/usr/bin/python# -*- coding:utf-8 -*-#author: wklken#desc: use to read db xml config.#-----------------------#2012-02-18 created#----------------------import sys,osfrom xml.dom import minidom, Nodedef 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 contentif __name__ == "__main__":read_dbconfig_xml(sys.argv[1])

Methods involved
Root = minidom. parse (xml_file_path) Get the dom object

Root. getElementsByTagName ("table") obtains the node list based on the tag.

Table. getAttribute ("name") Get attributes

Primary_key.getElementsByTagName ("name") [0]. childNodes [0]. nodeValue obtain the value of the subnode (id is obtained)

SAX
Requirement
Reads xml data files. The files are large and need to be inserted to the database in real time.

Xml document

 
    
   
    
100000
     
   
    
Male
   Beijing, Haidian District  
   
    
437
     
   1989  
   
    
333
     
   
    
242
     
   
    
Null
     
   
    
University
     
     
   
    
1
     
   
    
February 14
   
  
 

Processing
When processing a sax file, it does not read the file in a node-like dimension like dom. It can only end the tag with the start TAG content.

The processing idea is: through a handler, there is a processing function for each start tag, content, and end tag

Code and Annotation
Person processing class

From xml. sax import handler, parseStringclass PersonHandler (handler. contentHandler): def _ init _ (self, db_ops): # db op obj self. db_ops = db_ops # store the map self of a person. person = {}# current tag self. current_tag = "" # whether it is the content between tags. The content between tags is obtained for the purpose, and self is not disturbed by blank spaces. in_quote = 0 # Start, clear map def startElement (self, name, attr): # clear map if name = "person": self. person = {}# record status self. current_tag = name self. in_quote = 1 # End, insert database def endElement (self, name): # End with person indicates reading information of a person. 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) # process self. in_quote = 0 def characters (self, content): # if the content is between tags, update it to the map if self. in_quote: self. person. update ({self. current_tag: content })

Complete code for warehouse receiving

#! /Usr/bin/python #-*-coding: UTF-8-*-# parse_person.py # version: 0.1 # author: wukunliang@163.com # desc: parse person. xml and out sqlimport sys, osimport MySQLdbreload (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) "fields = (" id "," sex "," address "," fansNum "," summary "," wbNum "," gzNum "," blog "," edu ", "work", "renZh", "brithday") # database method 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(cmd.exe cute (SQL) return n Limit t MySQLdb. warning, e: print "Error: execute SQL '", SQL, "'failed' def close (self): self. conn. close () # person processing class from xml. sax import handler, parseStringclass PersonHandler (handler. contentHandler): def _ init _ (self, db_ops): # db op obj self. db_ops = db_ops # store the map self of a person. person = {}# current tag self. current_tag = "" # whether the content between tags is self. in_quote = 0 # Start, clear map def startElement (self, name, attr): # clear map if name = "person": self. person = {}# record status self. current_tag = name self. in_quote = 1 # End, insert database def endElement (self, name): # End with person indicates reading information of a person. 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) # process self. in_quote = 0 def characters (self, content): # if the content is between tags, update it to the map if self. in_quote: self. person. update ({self. current_tag: content}) if _ name _ = "_ main _": f = open (". /person. xml ") # If the source file gbk is transcoded as UTF-8, remove 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 ()

We usually use python to analyze data, tool scripts, and hadoop streamming. However, the usage and depth are insufficient, so we can only talk about it. We need to put it into practice.