How can I parse a Wikipedia XML dump with Python?

问题

I have:

import xml.etree.ElementTree as ET


def strip_tag_name(t):
    t = elem.tag
    idx = k = t.rfind("}")
    if idx != -1:
        t = t[idx + 1:]
    return t


events = ("start", "end")

title = None
for event, elem in ET.iterparse('data/enwiki-20190620-pages-articles-multistream.xml', events=events):
    tname = strip_tag_name(elem.tag)

    if event == 'end':
        if tname == 'title':
            title = elem.text
        elif tname == 'page':
            print(title, elem.text)

This seems to give the title just fine, but the page text always seems blank. What am I missing?

I haven't been able to open the file (it's huge), but I think this is an accurate snippet:

<mediawiki xmlns="http://www.mediawiki.org/xml/export-0.10/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mediawiki.org/xml/export-0.10/ http://www.mediawiki.org/xml/export-0.10.xsd" version="0.10" xml:lang="en">
  <siteinfo>
    <sitename>Wikipedia</sitename>
    <dbname>enwiki</dbname>
    <base>https://en.wikipedia.org/wiki/Main_Page</base>
    <generator>MediaWiki 1.29.0-wmf.12</generator>
    <case>first-letter</case>
    <namespaces>
      ...
    </namespaces>
  </siteinfo>
  <page>
    <title>AccessibleComputing</title>
    <ns>0</ns>
    <id>10</id>
    <redirect title="Computer accessibility" />
    <revision>
      <id>631144794</id>
      <parentid>381202555</parentid>
      <timestamp>2014-10-26T04:50:23Z</timestamp>
      <contributor>
        <username>Paine Ellsworth</username>
        <id>9092818</id>
      </contributor>
      <comment>add [[WP:RCAT|rcat]]s</comment>
      <model>wikitext</model>
      <format>text/x-wiki</format>
      <text xml:space="preserve">#REDIRECT [[Computer accessibility]]

\{\{Redr|move|from CamelCase|up\}\}</text>
      <sha1>4ro7vvppa5kmm0o1egfjztzcwd0vabw</sha1>
    </revision>
  </page>
  <page>
    <title>Anarchism</title>
    <ns>0</ns>
    <id>12</id>
    <revision>
      <id>766348469</id>
      <parentid>766047928</parentid>
      <timestamp>2017-02-19T18:08:07Z</timestamp>
      <contributor>
        <username>GreenC bot</username>
        <id>27823944</id>
      </contributor>
      <minor />
      <comment>Reformat 1 archive link. [[User:Green Cardamom/WaybackMedic_2.1|Wayback Medic 2.1]]</comment>
      <model>wikitext</model>
      <format>text/x-wiki</format>
      <text xml:space="preserve">
      ...
      </text>
    </revision>
  </page>
</mediawiki>

回答1:

The text refers to the text between the element tags (i.e. <tag>text</tag>) and not to all the child elements. Thus, in case of the title element one has:

<title>AccessibleComputing</title>

and the text between the tags is AccessibleComputing.

In the case of the page element, the only text defined is '\n ' and there are other child elements (see below), including the title element:

<page>
    <title>Anarchism</title>
    <ns>0</ns>
    <id>12</id>
    ... 
</page>

See more details in w3schools page

If you want to parse the file, I would recomend to use either findall method:

from lxml import etree
from lxml.etree import tostring

tree = etree.parse('data/enwiki-20190620-pages-articles-multistream.xml')
root = tree.getroot()
# iterate through all the titles
for title in root.findall(".//title", namespaces=root.nsmap):
    print(tostring(title))
    print(title.text)

which generates this output:

b'<title xmlns="http://www.mediawiki.org/xml/export-0.10/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">AccessibleComputing</title>\n    '
AccessibleComputing
b'<title xmlns="http://www.mediawiki.org/xml/export-0.10/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Anarchism</title>\n    '
Anarchism

or the xpath method:

nsmap = root.nsmap
nsmap['x'] = root.nsmap[None]
nsmap.pop(None)
# iterate through all the pages
for page in root.findall(".//x:page", namespaces=nsmap):
    print(page)
    print(repr(page.text)) # which prints '\n    '
    print('number of children: %i' % len(page.getchildren()))

and the output is:

<Element {http://www.mediawiki.org/xml/export-0.10/}page at 0x7ff75cc610c8>
'\n    '
number of children: 5
<Element {http://www.mediawiki.org/xml/export-0.10/}page at 0x7ff75cc71bc8>
'\n    '
number of children: 5

Please see lxml tutorial for more details.

回答2:

You are trying to get the content of the text property of the <page> element, but that is just whitespace.

To get the text of the <text> element, just change

elif tname == 'page':

elif tname == 'text':

回答3:

For XML parsing I use package untangle from PYPI, which presents a complete document view. Then you have:

import untangle

doc = untangle.parse('data/enwiki-20190620-pages-articles-multistream.xml')
for page in doc.mediawiki.page:
    print(page.title.cdata)
    for text in page.revision.text:
        print(text.cdata)

来源：https://stackoverflow.com/questions/56888333/how-can-i-parse-a-wikipedia-xml-dump-with-python

标签

python

xpath

elementtree