Python xml creation from list with element levels

Question

This is the first time i am working with xml processing.

The following python list contains all the elements/nodes that will used to create the final xml. Every item of the list is also a list composed of element/node and level pair.

For example:

['root', 1]

'root' is the name of the element, and 1 is level or position of 'root' in the xml tree.

[
['root', 1],
['dir', 2],
['book1',3],
['chapter1', 4],
['page1', 5],
['page2', 5],
['book2', 3],
['book3', 3],
['author', 3]
]

Following is the xml corresponding to above list

<root>
  <dir>
    <book1>
      <chapter1>
        <page1 para=4>
        <page2 para=5>
      </chapter1>
    </book1>
    <book2 para=3/>
    <book3 para=3/>
    <author name=abc>
  </dir>
</root>

The problem i am facing is, i don't know how to keep track of previous nodes so that new nodes are added into correct parent nodes?

For example:

should be added under

So during xml creation, after how to get/find parent node of so that child should be added at correct place?

Can anyone guide me to write a generic solution for this problem?

stew · Accepted Answer · 2011-12-13 21:00:46Z

1

keep a "lastforlevel" array which stores the last item appended at a given level. If you try create an element for level n, you need to append it to lastforlevel[n-1].

answered Dec 13, 2011 at 21:00

stew

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1 Comment

MA1 Over a year ago

Thanks, i will try it. Just a general question. What is the usual way to create xml? Do we have to keep track of every single node so that child nodes are placed at correct positions? OR It depends on the format of flat data?

yilmazhuseyin · Accepted Answer · 2011-12-13 21:11:49Z

0

I had the same problem last week. Here is my solution

http://www.yilmazhuseyin.com/blog/dev/convert-python-dict-xml/

Basic difference between your approach and mine is I used dicts instead of lists

answered Dec 13, 2011 at 21:11

yilmazhuseyin

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Comments

jterrace · Accepted Answer · 2011-12-13 21:29:23Z

Here's what I came up with:

xml_arr = [
['root', 1],
['dir', 2],
['book1',3],
['chapter1', 4],
['page1', 5],
['page2', 5],
['book2', 3],
['book3', 3],
['author', 3]
]

from xml.etree import ElementTree as etree

root = xml_arr.pop(0)
cur_level = root[1]
root = etree.Element(root[0])
cur_element = root
parents = [root]

for tag, level in xml_arr:
    while level < cur_level:
        cur_level -= 1
        parents.pop()
        cur_element = parents[-1]
    if level == cur_level:
        parents[-2].append(etree.Element(tag))
    if level > cur_level:
        cur_level = level
        new_elem = etree.Element(tag)
        cur_element.append(new_elem)
        parents.append(new_elem)
        cur_element = new_elem

print etree.tostring(root)

This prints:

<root><dir><book1><chapter1><page1 /><page2 /></chapter1></book1><book2 /><book3 /><author /></dir></root>

Or when pretty printed:

<root>
    <dir>
        <book1>
            <chapter1>
                <page1/>
                <page2/>
            </chapter1>
        </book1>
        <book2/>
        <book3/>
        <author/>
    </dir>
</root>

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