Python XML XPath partial failure message -

in code maintain there's xml parsing using minidom library.

for xml structure similar below:

<a val="a1">   <b val="b1">     <c val="c1">       data     </c>   </b> </a> 

code looks like:

for in doc.getelementsbytagname("a"):     aid = a.getattribute("val").encode('ascii')     if aid == aexpected:         afound =         break else: # not found     raise exception("no '%s' found" % aexpected) b in afound.getelementsbytagname("b"):     bid = b.getattribute("val").encode('ascii')     if bid == bexpected:         bfound = b         break else: # not found     raise exception("no b '%s' found" % bexpected) # similar c 

i wanted use xpath data. can (elementtree):

root.findall(".//a[@val=%s]/b[@val=%s]/c[@val=%s]" % (aexpected, bexpected, cexpected)) 

the code looks nicer now. but, when no data can found in xml, findall() returns none , have manually analyze file first non-matching element.

is there possibility in elementtree (or other xml api) both use xpath , have xpath returning first point of matching failure (similarly else clauses in original code)?

as pointed in 1 answer, code may substituted with:

afound = root.find(".//a[@val=%r]" % (aexpected,)) if not afound:     raise("a not present") bfound = afound.find("b[@val=%r]" % (bexpected,)) if not bfound:     raise("b not present") cfound = bfound.find("c[@val=%r]" % (cexpected,)) if not cfound:     raise("c not present") 

yes, that's cleaner original, looking library, give info me.

for following xml

    <a val="a1">   <b val="b1">     <c val="c1">       data     </c>   </b> </a> 

works code

import xml.etree.elementtree et  file = "sample.xml" aexpected = "a1" bexpected = "b1" cexpected = "c1"  tree = et.parse(file) root = tree.getroot()  bfound = root.find("./b[@val='" + bexpected + "']") cfound = root.find(".//c[@val='" + cexpected + "']")  print(root) print(bfound) print(cfound) 

output is:

<element 'a' @ 0x02919b10> <element 'b' @ 0x02919bd0> <element 'c' @ 0x02919c30> 

the xml.etree.elementtree not find xpath becouse root element

if want find element modify xml in following way

  <root> <a val="a1">   <b val="b1">     <c val="c1">       data     </c>   </b> </a> </root> 

and code

 import xml.etree.elementtree et  file = "sample.xml" aexpected = "a1" bexpected = "b1" cexpected = "c1"  tree = et.parse(file) root = tree.getroot()  afound = root.find("./a[@val='" + aexpected + "']") bfound = root.find(".//b[@val='" + bexpected + "']") cfound = root.find(".//c[@val='" + cexpected + "']")  print(afound) print(bfound) print(cfound) 

the result be

<element 'a' @ 0x02919b10> <element 'b' @ 0x02919bd0> <element 'c' @ 0x02919c30> 

best regards