Question

I have an XML file with the following structure:

<root>
  <subroot id="someID">
    <val1 value="a"/>
    <val2 value="b"/>
    <val3 value="c"/>
    <val4 value="1"/>
    <val5 value="2"/>
    <val6 value="3"/>
    <otherval value="xyz"/>
  </subroot>
  <subroot id="anotherID">
    <val1 value="aa"/>
    <val2 value="bb"/>
    <val3 value="cc"/>
    <val4 value="11"/>
    <val5 value="22"/>
    <val6 value="33"/>
    <otherval value="xxyyzz"/>
  </subroot>
  .
  .
  .
  .
</root>

I am trying to retrieve the values in each tag. For example, my desired output would be:

val1=a
val2=b
val3=c
val4=1
val5=2
val6=3
otherval=xyz

Here is my non-working code that produces blanks, ie val1="", val2=""...:

def getValues(self):
    from xml.dom.minidom import parseString
    import json

    file = open('myfile.xml','r')
    data = file.read()
    dom = parseString(data)
    rows = dom.getElementsByTagName("root")[0].getElementsByTagName("subroot")
    valueString = ""
    for row in rows:
        valueString = valueString+json.dumps(
        {
        'val1': row.getAttribute("val1"),
        'val2': row.getAttribute("val2"),
        'val3': row.getAttribute("val3"),
        'val4': row.getAttribute("val4"),
        'val5': row.getAttribute("val5"),
        'val6': row.getAttribute("val6"),
        'other': row.getAttribute("otherval")},
        sort_keys=True,
        indent=4)+","
    response_generator = ( "["+valueString[:-1]+"]" )
    return HttpResponse(response_generator)
    otherval=xyz

I know that thisactually produces JSON but thats not important. The important thing is being able to extract the values and then I can do whatever with them afterwards.

Can someone show me what I’m missing here?
Also, should I change my XML so all the val1,val2,val3.... are just called val?

Thanks.

Answer 1

My suggestion is to structure your data as follows:

<root>
  <subroot id="someID">
    <value id="1">a</value>
    <value id="2">b</value>
    <value id="3">c</value>
    <value id="4">d</value>
    <value id="5">2</value>
    <value id="6">3</value>
    <value id="other">xyz</value>
  </subroot>
  <subroot id="anotherID">
    <value id="1">aa</value>
    <value id="2">bb</value>
    <value id="3">cc</value>
    <value id="4">11</value>
    <value id="5">22</value>
    <value id="6">33</value>
    <value id="other">xxyyzz</value>
  </subroot>
</root>

Then, to parse, I suggest the etree library – it’s in the standard library for Python and I’ve found it far nicer to work with than anything else. It’s just a simple case of iterating through the subroots and value elements and extracting the data.

from xml.etree import ElementTree

xml = ElementTree.parse("test.xml")

root = xml.getroot()

all = {}

for group in root.findall("subroot"):
    temp = {}
    for value in group.findall("value"):
        temp[value.get("id")] = value.text
    all[group.get("id")] = temp

all will then be:

{'someID': {'1': 'a', '3': 'c', '2': 'b', '5': '2', '4': 'd', '6': '3', 'other': 'xyz'}, 'anotherID': {'1': 'aa', '3': 'cc', '2': 'bb', '5': '22', '4': '11', '6': '33', 'other': 'xxyyzz'}}

You could also do this as a dict comprehension:

all = {group.get("id"): {value.get("id"): value.text for value in group.findall("value")} for group in root.findall("subroot")}

Note that this is a little hard to read and will fall apart if you try to do anything more complex.