python - LXML:如何忽略未知的 namespace 前缀？

对于Crowdflower，我需要定义一个CML，因为它与我要使用的XML非常相似
LXML完成此任务。 Crowdflower为此定义了CML标签，例如：


<cml:textarea label="Sample text area:" />或
<cml:checkbox label="A single checkbox with a default value" />


（摘自Crowdflower网站：[1]）

而且，这些CML文件通常不使用根元素。当我尝试使用lxml创建CML元素时，它将引发一个XMLSyntaxError。我想使用Is there a switch to ignore undefined namespace prefixes in LXML?中的解决方案，但是创建的CML缺少根目录。

如何修改不忽略未知名称空间前缀的LXML？

码

from lxml import etree

txt = "An example label"
txt_elm = etree.fromstring('<cml:text label="%s" />' % txt)

错误信息

txt_elm = etree.fromstring('<cml:text label="%s" />' % txt)
File "lxml.etree.pyx", line 2994, in lxml.etree.fromstring (src/lxml/lxml.etree.c:63296)
File "parser.pxi", line 1617, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:93649)
File "parser.pxi", line 1495, in lxml.etree._parseDoc (src/lxml/lxml.etree.c:92453)
File "parser.pxi", line 1011, in lxml.etree._BaseParser._parseDoc (src/lxml/lxml.etree.c:89097)
File "parser.pxi", line 577, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:84804)
File "parser.pxi", line 676, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:85904)
File "parser.pxi", line 616, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:85228)
lxml.etree.XMLSyntaxError: Namespace prefix cml on text is not defined, line 1, column 16

例子1

<h2>Image 1 :</h2>
<img src="{{urlmedia1}}" width="450" height="300">

<h2>Image 2 :</h2>
<img src="{{urlmedia2}}" width="450" height="300">

<cml:radios label="Which one of these two images conveys the most {{axis}} ?" validates="required">
   <cml:radio label="Image 1"/>
   <cml:radio label="Image 2"/>
</cml:radios>

例子2

<p>Focus on the emotion you feel when watching these shots. Which one convey?    <b>{{axis}}</b> the most ?</p>
<p>While you have the right to watch the shots as many times as you want, you should focus on your first impression.</p>
<hr/>
    <p>video 1: <em>{{miscdata1}}</em></p>
    <object style="height: 300px; width: 490px">
      <param name="movie" value="{{urlmedia1}}" />
      <param name="allowFullScreen" value="true" />
      <param name="allowScriptAccess" value="always" />
      <embed src="{{urlmedia1}}" type="application/x-shockwave-flash" allowfullscreen="false" allowScriptAccess="always" width="490" height="300"/>
    </object>
<hr/>
    <p>video 2: <em>{{miscdata2}}</em></p>
    <object style="height: 300px; width: 490px">
      <param name="movie" value="{{urlmedia2}}" />
      <param name="allowFullScreen" value="true" />
      <param name="allowScriptAccess" value="always" />
      <embed src="{{urlmedia2}}" type="application/x-shockwave-flash" allowfullscreen="false" allowScriptAccess="always" width="490" height="300"/>
    </object>
<hr/>
<cml:radios label="Which one conveys {{axis}} the most?" validates="required">
  <cml:radio label="Shot 1" />
  <cml:radio label="Shot 2" />
</cml:radios>

这两个示例均来自：2

注意：我的目标是建立一个CML结构，而不是解析一个。

最佳答案

您可以使用ElementMaker（来自lxml）来简化此过程，如下所示：

from lxml.builder import ElementMaker
E = ElementMaker(namespace='cml', nsmap={'cml':'cml'})

cmlroot = E.root()
radios = E.radios(label='My question?', validates='required')
cmlroot.append(radios)
radios.append(E.radio(label='Image1'))
radios.append(E.radio(label='Image2'))

etree.dump(cmlroot)
<cml:root xmlns:cml="cml">
  <cml:radios validates="required" label="My question?">
    <cml:radio label="Image1"/>
    <cml:radio label="Image2"/>
  </cml:radios>
</cml:root>

然后，您可以通过删除第一行和最后一行来获取所需的文本。

还有其他处理方法，但是我认为这是最简单的方法。

这无助于解析，解析本身就是问题所在，但对于生成而言效果很好。