Python common built-in modules-xml module (detailed description), pythonxml

Python common built-in modules-xml module (detailed description), pythonxml

Xml can be used to tag data and define data types. It is a source language that allows you to define your own markup language. The structure is similar to HTML hypertext markup language. However, they are designed for different purposes. hypertext markup language is designed to display data, and its focus is on the appearance of the data. It is designed to transmit and store data, with the focus on data content. So how does Python process XML files? Let's take a look at the xml module of common Python built-in modules.

ElementTree is the XML processing module of python. It provides a lightweight object model. When using the ElementTree module, You need to import xml. etree. ElementTree. ElementTree indicates the entire XML node tree, while Element indicates a separate node in the number of nodes.

Construct an XML file

ElementTree (tag), where tag indicates the root node and initializes an ElementTree object.

The Element (tag, attrib = {}, ** extra) function is used to construct a root node of XML. tag indicates the name of the root node, and attrib is an optional function, attribute of a node.

SubElement (parent, tag, attrib = {}, ** extra) is used to construct a subnode Element of an existing node. text and SubElement. text indicates the additional content attribute of the element object, Element. tag and Element. attrib indicates the tag and attribute of the element object.

ElementTree. write (file, encoding = 'US-ascii ', xml_declaration = None, default_namespace = None, method = 'xml'), the function creates an xml file, write the number of nodes to the XML file.

The following code uses the sitemap. xml file of a new website as an example.

#! /Usr/bin/env python #-*-coding: UTF-8-*-from xml. etree import ElementTree as ETdef build_sitemap (): urlset = ET. element ("urlset") # Set a root node with the label urlset url = ET. subElement (urlset, "url") # create a subnode loc = ET under the root node urlset. subElement (url, "loc") loc. text = "http: // www/baidu.com" lastmod = ET. subElement (url, "lastmod") lastmod. text = "2017-10-10" changefreq = ET. subElement (url, "changefreq") changefreq. text = "daily" priority = ET. subElement (url, "priority") priority. text = "1.0" tree = ET. elementTree (urlset) tree. write ("sitemap. xml ") if _ name _ = '_ main _': build_sitemap ()

The result is shown in:

Parse and modify XML files

ElementTree. parse (source, parser = None ),Load the xml file and return the ElementTree object. Parser is an optional parameter. If it is null, the standard XMLParser parser is used by default.

ElementTree. getroot (),Get the root node. Returns the element Object of the root node.

Element. remove (tag ),Delete the following functions for sub-nodes named tag under root. All objects of ElementTree and Element contain.

Find (match ),Obtain the first child node that matches the match. match can be a tag name or path. Returns an element findtext (match, default = None). The findall (match) content of the first configured match element is obtained, match can be a tag or path. It will return a list containing the matching elements information iter (tag) and create an iterator with the current node as the root node.

Take sitemap. xml created above as an example to modify it. The code example is as follows:

#!/usr/bin/env python# -*- coding:utf-8 -*- from xml.etree import ElementTree as ETtree = ET.parse("sitemap.xml")url = tree.find("url")for rank in tree.iter('loc'):  rank.text = "http://www.adminba.com"tree.write("sitemap.xml")

The code above changes the url to a http://www.adminba.com. In addition, the node also has the set (set node attributes) and attrib (delete node attributes) methods.

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