new_process_xml.py

import copy
import xml.etree.ElementTree as etree


a = ['труба', 'светильник', 'кран шаровый']
b = [3, 2, 2]


tree = etree.parse('dop_raboty_kopia.xml')
root = tree.getroot()


chapter = root.find('.//Chapters/Chapter')
position = chapter.getchildren()[1]

for i in range(len(a)):
    new_position = copy.deepcopy(position)
    quantity = new_position.find('Quantity')
    quantity.attrib['Fx'] = str(b[i])
    new_position.attrib['Caption'] = a[i]
    chapter.insert(len(chapter.getchildren()), new_position)


tree.write('output.xml', encoding="windows-1251")