python 解析xml 檔案: DOM 方式

微微微笑發表於2015-12-31
PythonXML

環境

python：3.4.4

準備xml檔案

首先新建一個xml檔案，countries.xml。內容是在python官網上看到的。

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank>1</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank>4</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank>68</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

準備python檔案

新建一個test_DOM.py，用來解析xml檔案。

#!/usr/bin/python
# -*- coding: UTF-8 -*-

from xml.dom.minidom import parse
import xml.dom.minidom

DOMTree = xml.dom.minidom.parse("countries.xml")
collection = DOMTree.documentElement
if collection.hasAttribute("data"):
    print ("Root element : %s" % collection.getAttribute("data"))

countries = collection.getElementsByTagName("country")

for country in countries:
    print ("*****Country*****")
    if country.hasAttribute("name"):
        print ("Name: %s" % country.getAttribute("name"))
    rank = country.getElementsByTagName('rank')[0]
    print ("Rank: %s" % rank.childNodes[0].data)
    year = country.getElementsByTagName('year')[0]
    print ("Year: %s" % year.childNodes[0].data)
    gdppc = country.getElementsByTagName('gdppc')[0]
    print ("Gdppc: %s" % gdppc.childNodes[0].data)
    neighbors = country.getElementsByTagName('neighbor')
    for neighbor in neighbors:
        print ("Neighbor:", neighbor.getAttribute("name"),neighbor.getAttribute("direction"))

執行結果

>python test_DOM.py
*****Country*****
Name: Liechtenstein
Rank: 1
Year: 2008
Gdppc: 141100
Neighbor: Austria E
Neighbor: Switzerland W
*****Country*****
Name: Singapore
Rank: 4
Year: 2011
Gdppc: 59900
Neighbor: Malaysia N
*****Country*****
Name: Panama
Rank: 68
Year: 2011
Gdppc: 13600
Neighbor: Costa Rica W
Neighbor: Colombia E

備註

DOM（Document Object Model）

DOM是一個W3C的跨語言的API，用來讀取和更改 XML 文件。

一個DOM解析器在解析一個XML文件時，一次性讀取整個文件，把文件中的所有元素儲存在記憶體中的一個樹結構中，之後可以對這個樹結構進行讀取或修改，也可以把修改過的樹結構寫入xml檔案。

參見： https://docs.python.org/2/library/xml.dom.html

 

DOMTree = xml.dom.minidom.parse("countries.xml")

使用 xml.dom.minidom解析器開啟 countries.xml 檔案，並返回一個 Document物件，也就是樹結構。Document 物件代表了整個 XML 文件，包括它的元素、屬性、處理指令、備註等。

參見： https://docs.python.org/2/library/xml.dom.minidom.html

Return a Document from the given input. filename_or_file may be either a file name, or a file-like object. parser, if given, must be a SAX2 parser object. This function will change the document handler of the parser and activate namespace support; other parser configuration (like setting an entity resolver) must have been done in advance.

 

collection = DOMTree.documentElement

返回 DOMTree的根元素。

 

Document.documentElement
The one and only root element of the document.

 

rank = country.getElementsByTagName('rank')[0]

從country往下尋找所有 tag名為“rank”的元素節點，將找到的第一個節點賦值給 rank。

Document.getElementsByTagName(tagName)
Search for all descendants (direct children, children’s children, etc.) with a particular element type name.

 

collection.getAttribute("data")

獲取並返回 collection 的“data”屬性值。如果collection沒有“data”屬性，則返回一個空的字串。

Element.getAttribute(name)
Return the value of the attribute named by name as a string. If no such attribute exists, an empty string is returned, as if the attribute had no value.

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