如何使用python解析具有深层结构的xml字符串

How to parse xml string having deep structures using python

这里也提出了类似的问题(PythonXML解析)，但我无法访问感兴趣的内容。

如果classification-scheme标记值为CPC，我需要提取标记patent-classification之间包含的所有信息。有多个这样的元素，并被封装在patent-classifications标记内。

在下面给出的示例中，有三个这样的值：C 07 K 16 22 I、A 61 K 2039 505 A和C 07 K 2317 21 A。

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<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="/3.0/style/exchange.xsl"?>
<ops:world-patent-data xmlns="http://www.epo.org/exchange" xmlns:ops="http://ops.epo.org" xmlns:xlink="http://www.w3.org/1999/xlink">
<ops:meta name="elapsed-time" value="21"/>
<exchange-documents>
<exchange-document system="ops.epo.org" family-id="39103486" country="US" doc-number="2009234106" kind="A1">
<bibliographic-data>
<publication-reference>
<document-id document-id-type="docdb">
<country>US</country>
<doc-number>2009234106</doc-number>
<kind>A1</kind>
<date>20090917</date>
</document-id>
<document-id document-id-type="epodoc">
<doc-number>US2009234106</doc-number>
<date>20090917</date>
</document-id>
</publication-reference>
<classifications-ipcr>
<classification-ipcr sequence="1">
<text>C07K 16/ 44 A I </text>
</classification-ipcr>
</classifications-ipcr>
<patent-classifications>
<patent-classification sequence="1">
<classification-scheme office="" scheme="CPC"/>
<section>C</section>
<class>07</class>
<subclass>K</subclass>
<main-group>16</main-group>
<subgroup>22</subgroup>
<classification-value>I</classification-value>
</patent-classification>
<patent-classification sequence="2">
<classification-scheme office="" scheme="CPC"/>
<section>A</section>
<class>61</class>
<subclass>K</subclass>
<main-group>2039</main-group>
<subgroup>505</subgroup>
<classification-value>A</classification-value>
</patent-classification>
<patent-classification sequence="7">
<classification-scheme office="" scheme="CPC"/>
<section>C</section>
<class>07</class>
<subclass>K</subclass>
<main-group>2317</main-group>
<subgroup>92</subgroup>
<classification-value>A</classification-value>
</patent-classification>
<patent-classification sequence="1">
<classification-scheme office="US" scheme="UC"/>
<classification-symbol>530/387.9</classification-symbol>
</patent-classification>
</patent-classifications>
</bibliographic-data>
</exchange-document>
</exchange-documents>
</ops:world-patent-data>

如果没有，请安装漂亮的汤：

$ easy_install BeautifulSoup4。

试试这个：

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from bs4 import BeautifulSoup

xml = open('example.xml', 'rb').read()
bs = BeautifulSoup(xml)

# find patent-classification
patents = bs.findAll('patent-classification')
# filter the ones with CPC
for pa in patents:
if pa.find('classification-scheme', {'scheme': 'CPC'} ):
print pa.getText()