解析XML: Python ElementTree，查找元素及其父元素，同父元素不包含其他元素

Question

I am using python's ElementTree library to parse an XML file which has the following structure. I am trying to get the xml string corresponding to entity with id = 192 with all its parents (folders) but without other entities

   <catalog>
        <folder name="entities">
            <entity id="102">

            </entity>
            <folder name="newEntities">
                <entity id="192">

                </entity>

                <entity id="2982">

                </entity>
            </folder>
        </folder>
    </catalog>

The required result should be

    <catalog>
        <folder name="entities">
            <folder name="newEntities">
                <entity id="192">

                </entity>
            </folder>
        </folder>
    </catalog>

assuming the 1st xml string is stored in a variable called xml_string

tree = ET.fromstring(xmlstring)
id = 192
required_element = tree.find(".//entity[@id='" + id + "']")

This gets the xml element for the required entity but not the parent folders, any quick solution fix for this?

Answer 1

The challenge here is to bypass the fact that ET has no parent information. The solution is to use parent_map

import copy
import xml.etree.ElementTree as ET
import xml.dom.minidom as minidom

xml = '''<catalog>
        <folder name="entities">
            <entity id="102">

            </entity>
            <folder name="newEntities">
                <entity id="192">

                </entity>

                <entity id="2982">

                </entity>
            </folder>
        </folder>
    </catalog>'''


def prettify(elem):
    """Return a pretty-printed XML string for the Element.
    """
    rough_string = ET.tostring(elem, 'utf-8')
    reparsed = minidom.parseString(rough_string)
    return reparsed.toprettyxml(indent="\t")

root = ET.fromstring(xml)
parent_map = {c: p for p in root.iter() for c in p}
_id = 192
required_element = root.find(".//entity[@id='" + str(_id) + "']")
_path = [copy.deepcopy(required_element)]
while True:
    parent = parent_map.get(required_element)
    if parent:
        _path.append(copy.deepcopy(parent))
        required_element = parent
    else:
        break
idx = len(_path) - 1
while idx >= 1:
    _path[idx].clear()
    _path[idx].append(_path[idx-1])
    idx -= 1

print(prettify(_path[-1]))

output

<?xml version="1.0" ?>
<catalog>
    <folder>
        <folder>
            <entity id="192">

                </entity>



        </folder>
    </folder>
</catalog>