Python Lxml：将自己的标签添加到XML文件

Question

I've got a problem while adding my own Elements (tags) to an XML tree I've parsed from a file.

If I'm trying to add a Element to the existing tree, that one from the file, it doesn't add it correctly, no matter if I use new_tag = etree.Subelement(self.root, "new_tag") or
new_tag = Element("new_tag") self.root.append(new_tag)

The returning of self.root.tostring() is looking awesome, the added elements where not indented in the right way and for example len(self.root) still returns the same value as it did before I added the Element.

The only thing I did diffrent from the examples at lxml.de is that I put all these thing into a class ... but why shouldn't that work?

I hope you could help me, because I was searching for that bug about 3 hours and I didn't find it.

Leon

edit:

here is the code:

#!/usr/bin/env python3

from lxml import etree

class MyClass(object):
    def __init__(self, xml_filepath = "data.xml"):
        '''
        Constructor
        '''
        self._xml_path = xml_filepath

        with open(self._xml_path) as input_file:
            self.tree = etree.parse(input_file)
        self.xml_tags = self.tree.getroot()[0]

    def read_something(self):


        return [tag.tag for tag in self.tree.iter("child")]

    def change_something(self):
        self.xml_tags[0].tag = "test"

    def add_something(self):
        for elements in self.tree.iter('Home'):        
            child = etree.Element("child")
            child2 = etree.Element("child2")
            elements.insert(1,child)
            child.insert(0, child2)
            child2.text = "23123"

    def to_string(self):
        list_ = list(self.tree.getroot()[0])
        print(list_)
        return(etree.tostring(self.tree, pretty_print=True, xml_declaration=True).decode())

if __name__ == '__main__':
    testClass = MyClass()
    testClass.change_something()
    testClass.add_something()
    print(testClass.to_string())
    print(testClass.read_something())

the returning is:

[<Element test at 0x765e7e68>, <Element child at 0x765e7e90>]
<?xml version='1.0' encoding='ASCII'?>
<root>
  <Home>
    <test>
      <name>Hello world</name>
    </test>
  <child><child2>23123</child2></child></Home>
</root>

['child']

and the original xml file:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <Home>
    <test>      
      <name>Hello world</name>
    </test>    
  </Home>
</root>

Answer 1

You have to directly find the root and then insert. The tutorial you are looking at does not parse an example xml file but actually creates root and child elements:

import lxml.etree as ET

dom = ET.parse('C:\Path\To\XMLFile.xml')

for elements in dom.iter('root'):        
    child = ET.Element("child")
    elements.insert(1,child)
    child.text = '...'

Answer 2

I've got found the Error by myself. If I add my own parser to the parse method, I'll get a well formated XML output, also the interna are working well now.