Python LXML-获取标签文本的索引 [英] Python lxml - get index of tag's text

问题描述

我有一个格式类似于docx的xml文件，即:

I have an xml-file with a format similar to docx, i.e.:

<w:r>
  <w:rPr>
    <w:sz w:val="36"/>
    <w:szCs w:val="36"/>
  </w:rPr>
  <w:t>BIG_TEXT</w:t>
</w:r>

我需要在源xml中获得"BIG_TEXT"的索引，例如:

I need to get an index of "BIG_TEXT" in source xml, like:

from lxml import etree
text = open('/devel/tmp/doc2/word/document.xml', 'r').read()

root = etree.XML(text)

start = 0
for e in root.iter("*"):
    if e.text:
        offset = text.index(e.text, start)
        l = len(e.text)
        print 'Text "%s" at offset %s and len=%s' % (e.text, offset, l)
        start = offset + l

我可以从当前索引+ len(text)的位置开始新的搜索，但是还有另一种方法吗?元素可以有一个字符，例如w.它将找到w的索引，但不会找到标签文本w的索引.

I can start a new search from position of current index + len(text), but is there another way? Element may have one character, w for example. It will find index of w, but not index of tag text w.

推荐答案

我一直在寻找类似的解决方案(在大型xml文件中为节点建立索引以便快速查找).

I was looking for a similar solution (indexing nodes in a big xml file for fast lookup).

• AFAIK，lxml仅提供源代码行，这是不够的. cf API :Original line number as found by the parser or None if unknown.
• 但是expat在文件中提供了确切的偏移量: CurrentByteIndex> CurrentByteIndex .
  • 从start_element处理程序中获取，它返回标签的开始(即'<')偏移量.
  • 从char_data处理程序中获取，它返回数据的起始偏移量(在您的示例中为'B').
  • AFAIK, lxml only offers sourceline, which is insufficient. Cf API : Original line number as found by the parser or None if unknown.
  • But expat provides the exact offset in the file : CurrentByteIndex.
    • Fetched from start_element handler, it returns tag's start (ie '<') offset.
    • Fetched from char_data handler, it returns data's start (ie 'B' in your example) offset.

    示例:

    import xml.parsers.expat
    
    # handler functions for parser events, and housekeeping.
    class handler :
       def __init__(self, current_parser) :
          #tag of interest
          self.TARGET_TAG = "w:t"
    
          #set up parser
          self.parser = current_parser
          self.parser.StartElementHandler  = self.start_element
          self.parser.EndElementHandler    = self.end_element
          self.parser.CharacterDataHandler = self.char_data
    
          self.target_tag_met = False
          self.index = None
    
       def start_element(self, name, attrs):
          self.target_tag_met = (name == self.TARGET_TAG)
    
       def end_element(self, name) :
          self.target_tag_met = False
    
       def char_data(self, data):
          if self.target_tag_met :
             self.index = self.parser.CurrentByteIndex
    
    #open file in binary mode for robuster byte offsets.
    xmlFile = open("so_test.xml", 'rb')
    
    p = xml.parsers.expat.ParserCreate()
    h = handler(p)
    
    p.ParseFile(xmlFile)
    print (h.index)
    

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