python XML查找和替换

Question

After fighting a day with python / etree without considerable success:

I have a xml file (items.xml)

<symbols>
    <symbol>
        <layer class="SvgMarker">
            <prop k="size" v="6.89"/>
        </layer>
    </symbol>
    <symbol>
        <layer class="SvgMarker">
            <prop k="size" v="3.56"/>
        </layer>
    </symbol>
    <symbol>
        <layer class="line">
            <prop k="size" v="1"/>
        </layer>
    </symbol>            
</symbols>

Questions

1. read this file
2. find all prop elements which have a parent element namend "layer" with class "SvgMarker"
3. multiply the value of v with 1.5
4. write the content back

I do not stick on etree if there is something easier.

Answer 1

This would help you

import xml.etree.ElementTree as ET

tree = ET.parse('items.xml') # Path to input file
root = tree.getroot()

for prop in root.iter('.//*[@class="SvgMarker"]/prop'):
   prop.set('v', str(float(prop.get('v')) * 1.5))

tree.write('out.xml', encoding="UTF-8")

Ref: https://docs.python.org/2/library/xml.etree.elementtree.html#example

Answer 2

You need to take care of hierarchy in xml tags and their type conversion to perform multiplication. I tested below code with your xml, it works fine.

import xml.etree.ElementTree as ET
tree = ET.parse('homemade.xml')                 #Step 1
root = tree.getroot()
for symbol in tree.findall('symbol'):
    for layer in symbol.findall('layer'):
        class_ = layer.get('class')
        if(class_=="SvgMarker"):                #Step 2
            for prop in layer.findall('prop'):
                new_v = prop.get('v')
                new_v = float(new_v)*1.5        #Step 3
                prop.set('v',str(new_v))
outFile = open('homemade.xml', 'w')
tree.write(outFile)                             #Step 4

Hope this helps.