元素树：如何查找具有相同属性值的所有下一个子元素

Question

I have an XML file with following structure:

<?xml version="1.0"?>
<data>
<product>
    <Product_Code>code1</Product_Code>
    <Size>x</Size>
    <Quantity>1<Quantity>
</product>
<product>
    <Product_Code>code3</Product_Code>
    <Size>c</Size>
    <Quantity>5<Quantity>
</product>
<product>
    <Product_Code>code2</Product_Code>
    <Size>z</Size>
    <Quantity>2<Quantity>
</product>
<product>
    <Product_Code>code3</Product_Code>
    <Size>a</Size>
    <Quantity>1<Quantity>
</product>
<product>
    <Product_Code>code1</Product_Code>
    <Size>y</Size>
    <Quantirt>1<Quantity>
</product>
<product>
    <Product_Code>code3</Product_Code>
    <Size>b</Size>
    <Quantity>5<Quantity>
</product>
</data>

There are products in the XML. Each product has a code,size and quantoty. Code can be common.

I want to select all different size corresponding to each code and quantity corresponding to each size. I want to do it on the go. Eg If iterate through the child elements as and find an element with code = "code1", I'd like to find all other elements in the root withcode = "code1" and their corresponding size and quantity value.

The actual proble is to generate following XML:

<products>
    <product>
        <Product_Code>code1<Product_Code>
        <variants>
            <variant>
                <size>x</size>
                <quantity>1</quantity>
            </variant>
            <variant>
                <size>y</size>
                <quantity>1</quantity>
            </variant>
        </variants>
    </product>
    <product>
        <Product_Code>code2<Product_Code>
        <variants>
            <variant>
                <size>z</size>
                <quantity>2</quantity>
            </variant>
        </variants>
    </product>
    <product>
        <Product_Code>code3<Product_Code>
        <variants>
            <variant>
                <size>a</size>
                <quantity>1</quantity>
            </variant>
            <variant>
                <size>b</size>
                <quantity>5</quantity>
            </variant>
            <variant>
                <size>c</size>
                <quantity>5</quantity>
            </variant>
        </variants>
    </product>
</products>

Answer 1

This is the best I have right now for it being rather late in the evening or morning, depending on how you look at it. There will likely need to be some optimization if you are doing this on a large amount of XML, but this should get the job done for now and will work on Python 2.7+.

This solution uses a dictionary to aggregate the products together and create the variants sub-element. Then it iterates through the dictionary to create the new tree with the product code, and variants as children.

import xml.etree.ElementTree as etree

tree = etree.parse('test.xml')
root = tree.getroot()
products = dict()
newroot = etree.Element('products')

for product in root.iterfind("product"):
    product_code = product.find('Product_Code')
    product.remove(product_code)
    product.tag = "variant"
    variants = products.setdefault(product_code.text, 
                                   etree.Element("variants"))
    variants.append(product)

for product in products:
    product_element = etree.Element('product')
    product_code = etree.Element('Product_Code')
    product_code.text = product
    product_element.append(product_code)
    product_element.append(products[product])
    newroot.append(product_element)

result_xml = etree.tostring(newroot)