使用lxml解析大型XML [英] Parse large XML with lxml
问题描述
我正在尝试使脚本工作.到目前为止,它什么都没输出.
I am trying to get my script working. So far it doesn't managed to output anything.
这是我的test.xml
This is my test.xml
<mediawiki xmlns="http://www.mediawiki.org/xml/export-0.8/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mediawiki.org/xml/export-0.8/ http://www.mediawiki.org/xml/export-0.8.xsd" version="0.8" xml:lang="it">
<page>
<title>MediaWiki:Category</title>
<ns>0</ns>
<id>2</id>
<revision>
<id>11248</id>
<timestamp>2003-12-31T13:47:54Z</timestamp>
<contributor>
<username>Frieda</username>
<id>0</id>
</contributor>
<minor />
<text xml:space="preserve">categoria</text>
<sha1>0acykl71lto9v65yve23lmjgia1h6sz</sha1>
<model>wikitext</model>
<format>text/x-wiki</format>
</revision>
</page>
</mediawiki>
这是我的代码
from lxml import etree
def fast_iter(context, func):
# fast_iter is useful if you need to free memory while iterating through a
# very large XML file.
#
# http://www.ibm.com/developerworks/xml/library/x-hiperfparse/
# Author: Liza Daly
for event, elem in context:
func(elem)
elem.clear()
while elem.getprevious() is not None:
del elem.getparent()[0]
del context
def process_element(elem):
if elem.ns.text == '0':
print elem.title.text
context=etree.iterparse('test.xml', events=('end',), tag='page')
fast_iter(context, process_element)
我没有任何错误,只是没有输出.我想得到的是解析元素是否为0.
I don't get any error, simply there's no output. What I want to get is to parse the element if is 0.
推荐答案
您正在解析一个带名称空间的文档,并且不存在'page'
标记,因为该标记仅适用于没有标记的空间
You are parsing a namespaced document, and there is no 'page'
tag present, because that only applies to tags without a namespace.
您正在寻找包含'{http://www.mediawiki.org/xml/export-0.8/}ns'
元素的'{http://www.mediawiki.org/xml/export-0.8/}page'
元素.
You are instead looking for the '{http://www.mediawiki.org/xml/export-0.8/}page'
element, which contains a '{http://www.mediawiki.org/xml/export-0.8/}ns'
element.
许多lxml
方法确实允许您指定名称空间映射以使匹配更容易,但不幸的是iterparse()
方法不是其中之一.
Many lxml
methods do let you specify a namespace map to make matching easier, but the iterparse()
method is not one of them, unfortunately.
以下.iterparse()
调用肯定会处理正确的page
标签:
The following .iterparse()
call certainly processes the right page
tags:
context = etree.iterparse('test.xml', events=('end',), tag='{http://www.mediawiki.org/xml/export-0.8/}page')
,但是您需要使用.find()
来获取页面元素上的ns
和title
标签,或者使用xpath()
调用来直接获取文本:
but you'll need to use .find()
to get the ns
and title
tags on the page element, or use xpath()
calls to get the text directly:
def process_element(elem):
if elem.xpath("./*[local-name()='ns']/text()=0"):
print elem.xpath("./*[local-name()='title']/text()")[0]
在您的输入示例中显示为
:
which, for your input example, prints:
>>> fast_iter(context, process_element)
MediaWiki:Category
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