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XPath -count no. of specific tag occurences

Posted on 2004-09-25
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Last Modified: 2012-05-05
I am using libxml2 library in C to parse an xml document.  I am trying to count the no. of tags <Book>.  I tried using
"count(//Book)".  But I want the number rather than the node-set.   Is there an xpath expression to do this?

<?xml version="1.0" ?>
- <Book List>
- <Book>
  <Name>book1</Name>
  <Author>author1</Author>
  <Price>15.00</Price>  
  </Book>
- <Book>
  <Name>book2</Name>
  <Author>author2</Author>
  <Price>10.00</Price>  
  </Book>
  </Book List>

Thanks
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Question by:inquisitive123
2 Comments
 
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Assisted Solution

by:Praesidium
Praesidium earned 250 total points
ID: 12153891
XmlNode[] full = new XmlNode[full.Count];

Seems like this should work for you, count the number of nodes in your node list...  Why do you want the number of nodes, because depending on what you are doing, I may be able to offer you a better alternative...
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rdcpro earned 250 total points
ID: 12155402
Well, count(//Book) *is* an XPath eppression that does this.  Well, rather it's an XSLT expression that uses XPath.  But, I don't think there are any methods in Libxml that don't return nodesets...That is, in XSLT such an XPath expression will return a number but using DOM methods, it's not allowed.  You can get the nodelist, then use the DOM length property--this is the standard way of doing it.  I'm not a C programmer, but in Python (using the XPath wrappers for libxml2):

import libxml2

doc = libxml2.parseFile("tst.xml")
ctxt = doc.xpathNewContext()
res = ctxt.xpathEval("//book")
if len(res) != 2:
    print "XPath Query did not return the expected node set"
    sys.exit(1)
doc.freeDoc()
ctxt.xpathFreeContext()

Note that you must explicitly free both the document and the context.

Regards,
Mike Sharp
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