Select a node with a particular element value in XML using python 2.7 and XML element tree

Question

I've been struggling with this all morning and I haven't been able to get it to work.

I have an XML like this(stripped down anonymized version):

<?xml version="1.0" encoding="UTF-8"?>
<Root>
  <First_Level_Node>
    <Element_Name>
      <attribute1>1</attribute1>
      <attribute2>2</attribute2>
      <attribute3>3</attribute3>
      <attribute4>4</attribute4>
      <attribute5>5</attribute5>
      <attribute6>6</attribute6>
    </Element_Name>
    <Element_Name>
      <attribute1>42</attribute1>
      <attribute2></attribute2>
      <attribute3>NO</attribute3>
      <attribute4>42</attribute4>
      <attribute5>random value</attribute5>
      <attribute6>18th Jun 2014  07:09:18 GMT</attribute6>
    </Element_Name>
    <Element_Name>
      <attribute1>42</attribute1>
      <attribute2></attribute2>
      <attribute3>NO</attribute3>
      <attribute4>42</attribute4>
      <attribute5>random</attribute5>
      <attribute6>23rd Jul 2014  02:47:10 GMT</attribute6>
    </Element_Name>
    <Element_Name>
      <attribute1>42</attribute1>
      <attribute2></attribute2>
      <attribute3>NO</attribute3>
      <attribute4>42</attribute4>
      <attribute5>random</attribute5>
      <attribute6>08th Nov 2014  23:53:31 GMT</attribute6>
    </Element_Name>
  </First_Level_Node>
</Root>

Now I am already getting some values from all the elements and using them.

But now I want to select only the elements which have a certain attribute value pair.

For example in the xml I have pasted I need to get the elements only with attribute4 = 42

My current code is as follows:

tree=ET.parse('xmlname.xml')
root=tree.getroot()
for slot in input_data:
        for child in root[0]:
            for ch in child.findall('First Level Node/*/[@attribute4="' + str(sys.argv[1]) + '"]'):
                print ch
                if ch.tag == slot:
                    if ch.text == 'UNCOMPUTED' or ch.text == None:
                        slot_text.append("Undefined")
                    else:
                        slot_text.append(ch.text)
        data[slot]=Counter(slot_text).most_common()

But I don't get any values in ch. I have tried multiple variations of the same and all the Xpath I know, still no result.

Any help will be much appreciated.

NOTE: Element_Name is dynamic and can change.

EDIT: Tried this but am getting wrong info as output.

for slot in input_data:
        for child in root[0]:
            for ch in child:
                if ch.text == '42' and ch.tag == "attribute4":
                    flag=1
                if ch.tag == slot and flag == 1:
                    flag=0
                    if ch.text == 'UNCOMPUTED' or ch.text == None:
                        slot_text.append("Undefined")
                    else:
                        slot_text.append(ch.text)
        data[slot]=Counter(slot_text).most_common()

har07 · Accepted Answer · 2015-04-09 07:42:23Z

1

<attribute4> is an XML element, not XML attribute. So, the first thing I will try is the following XPath :

.....
xpath = 'First Level Node/*[attribute4="' + str(sys.argv[1]) + '"]'
for ch in child.findall(xpath):
......

_{*) side note: "First Level Node" is not a valid XML element example as it contains white-spaces}

UPDATE :

Speaking in the context of your XML sample, child variable already point to <First_Level_Node>, which is the children of <Root> :

for child in root[0]:

therefore, you need to remove First_Level_Node from the XPath :

.....
xpath = '*[attribute4="' + str(sys.argv[1]) + '"]'
for ch in child.findall(xpath):
......

edited Apr 9, 2015 at 7:42

answered Apr 8, 2015 at 10:30

har07

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8 Comments

Karanpreet Singh Over a year ago

I already tried that one with no result.(Also the "First Level Node" is actually not called that, the actual data has no spaces.)

har07 Over a year ago

@KaranpreetSingh Okay, It is good to strip down your XML to simpler, but keep it correct and still preserve the problem so we can analyze what make it behave that way : Short, Self Contained, Correct (Compilable), Example. Otherwise, only wild guesses...

lapinkoira Over a year ago

Dude you have the answer below, just replace this unreadable line for ch in child.findall('First Level Node/*/[@attribute4="' + str(sys.argv[1]) + '"]'): with this if ch.tag == "attribute4" and ch.text == "42" and you will have all the elements only with attribute4 = 42

Karanpreet Singh Over a year ago

I tried the xpath query in an online xpath tester and it works but i can't seems to get it work in the findall() call.

har07 Over a year ago

@KaranpreetSingh what happen if you try using the XML version posted in question? If the problem still there, then we have chance to analyze and suggest a solution, otherwise please edit your sample XML first...

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lapinkoira · Accepted Answer · 2015-04-08 13:51:14Z

0

Try this:

tree=ET.parse('xmlname.xml')
root=tree.getroot()

for first_level_node in root:
    for element_name in first_level_node:
        for attribute in element_name:
            if attribute.tag == "attribute4" and attribute.text == "42":
            # do something

edited Apr 8, 2015 at 13:51

answered Apr 8, 2015 at 10:38

lapinkoira

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9 Comments

Mathias Müller Over a year ago

Could you add an explanation for why the original code does not work, whereas yours does? Code-only answers do not help much.

lapinkoira Over a year ago

I am just looping through the tree assuming the tree will always have the same number of levels. I cant tell you why his code isnt working because his code is incomplete/with errors. First of all input_data is not defined, also children are nested so with root[0] you are skipping one level making it unreadable, and if he just wants to read all the elements with the text value equal to 42 I thought .text would be easier instead the findall pattern

lapinkoira Over a year ago

Also I missed to check the attribute.tag is equal to attribute4, will edit my answer

Karanpreet Singh Over a year ago

@lapinkoira I have defined input_data in the code before and it is not related to the xml hence I didn't expand on that further.

Karanpreet Singh Over a year ago

@lapinkoira Also I want to read the other elements in that node not the one I'm comparing for equality condition. For example if attribute4 == 42 then I want to get the values of atribute1 through 6 except 4 of course for that element_name. Also could you please clarify if you intend to have the "if ch.tag == slot: #code part of if" in place of the "#do something" or the for loop iterating through attributes?

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