python merge xml files

Question

Say input a.xml:

<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a">
        <permission name="x"/>
        <permission name="y"/>
  </privapp-permissions>
</permissions>

And b.xml:

<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a">
        <permission name="x"/>
        <permission name="z"/>
  </privapp-permissions>
</permissions>

Expected output c.xml:

<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a">
        <permission name="x"/>
        <permission name="y"/>
        <permission name="z"/>
  </privapp-permissions>
</permissions>

I write below code but it just append it not merge:

import xml.etree.ElementTree as ET

fname1 = "a.xml"
fname2 = "b.xml"
fname3 = "c.xml"

tree1 = ET.parse(fname1)
root1 = tree1.getroot()

tree2 = ET.parse(fname2)
root2 = tree2.getroot()

merged_tree = ET.ElementTree(ET.Element('root'))

merged_tree.getroot().append(root1)
merged_tree.getroot().append(root2)

merged_tree.write(fname3, encoding='utf-8')

Answer 1

You can manage the duplicates with a list:

import xml.etree.ElementTree as ET


a= """<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a">
        <permission name="x"/>
        <permission name="y"/>
  </privapp-permissions>
</permissions>"""

b= """<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a">
        <permission name="x"/>
        <permission name="z"/>
  </privapp-permissions>
</permissions>"""

c= """<?xml version="1.0" encoding="utf-8"?>
<permissions>
  <privapp-permissions package="a" />
</permissions>"""

tree = ET.fromstring(a)
tree1 = ET.fromstring(b)
l1 = tree.findall('.//permission')
l2 = tree1.findall('.//permission')

tree2 = ET.fromstring(c)

new = tree2.find('privapp-permissions')
new.extend(l1)
new.extend(l2)

d = []
for elem in tree2.iter('permission'):
    if elem.get('name') not in d:
        d.append(elem.get('name'))

for parent in tree2.findall('.//privapp-permissions'):
    for elem in tree2.iter('permission'):
        if elem.get('name') in d:
            d.remove(elem.get('name'))
        else:
            parent.remove(elem)
                          
root = ET.ElementTree(tree2)
ET.indent(root, space="  ", level=0)
#root.write(file_name, xml_declaration = True, encoding="utf-8")
ET.dump(root)

Output:

<permissions>
  <privapp-permissions package="a">
    <permission name="x" />
    <permission name="y" />
    <permission name="z" />
  </privapp-permissions>
</permissions>