使用 lxml 将一个 xml 复制到 python 中的另一个

Question

我在 python

中有以下代码

from lxml import etree

offers = etree.parse(r'prices.xml')

print("offers\n")

target = offers.xpath('//offer[./vendor/text()="Qtap"]')
length = len(target)
for i in  range(length):
    print(target[i])
    etree.ElementTree(target[i]).write('output.xml', encoding='utf-8', xml_declaration=True)

我只是阅读了 xml 文件。使用 xpath 从中读取数据并希望将所有数据写入另一个文件。大约有 2000 个元素显示为长度，但脚本只写最后一个。抱歉，我知道我的问题很愚蠢，但这是我在 Python.

上的第一个程序

尽管接受的答案确实有效。我要放 xml 文件的简单示例。作为输入，我得到了类似的东西：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<yml_catalog date="2022-02-16 18:16">
    <shop>
        <purchase_currencies>
            <currency id="USD" rate="28.3"/>
            <currency id="EUR" rate="32.18"/>
            <currency id="UAH" rate="1"/>
        </purchase_currencies>
        <categories></categories>
        <offers>
            <offer id="SD00025386">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/9/19289.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/9/19289/19289_1.jpg</picture>
                <name>Трап ANI Plast TA1612 горизонтальний з нержавіючою решіткою 150x150</name>
                <available>true</available>
                <oldCode>19289</oldCode>
                <model>TA1612</model>
                <purchase_price>405.158</purchase_price>
                <currency>UAH</currency>
                <retail_price>691</retail_price>
                <retail_oldprice></retail_oldprice>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="1"></outlet>
                    <outlet id="86" name="Київ" instock="3"></outlet>
                    <outlet id="87" name="Україна" instock="16"></outlet>
                </outlets>
                <vendor>Ани Пласт</vendor>
                <vendorCode>SD00025386</vendorCode>
            </offer>
            <offer id="SD00025387">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/9/19290.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/9/19290/19290_1.jpg</picture>
                <name>Трап ANI Plast TA1712 вертикальний з нержавіючою решіткою 150х150</name>
                <available>true</available>
                <oldCode>19290</oldCode>
                <model>TA1712</model>
                <purchase_price>354.843</purchase_price>
                <currency>UAH</currency>
                <retail_price>605</retail_price>
                <retail_oldprice></retail_oldprice>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="20"></outlet>
                    <outlet id="86" name="Київ" instock="3"></outlet>
                    <outlet id="87" name="Україна" instock="20"></outlet>
                </outlets>
                <vendor>Ани Пласт</vendor>
                <vendorCode>SD00025387</vendorCode>
            </offer>
<offer id="SD00022605">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_1.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_2.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_3.jpg</picture>
                <name>Донний клапан для раковини Qtap L02 з переливом</name>
                <available>true</available>
                <oldCode>16508</oldCode>
                <model>QTL02</model>
                <purchase_price>4.635</purchase_price>
                <currency>EUR</currency>
                <retail_price>261</retail_price>
                <retail_oldprice/>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="0"/>
                    <outlet id="86" name="Київ" instock="0"/>
                    <outlet id="87" name="Україна" instock="3"/>
                </outlets>
                <vendor>Qtap</vendor>
                <vendorCode>SD00022605</vendorCode>
            </offer>
            <offer id="SD00022606">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16509.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16509/16509_1.jpg</picture>
                <name>Донний клапан для раковини Qtap L01 з переливом</name>
                <available>true</available>
                <oldCode>16509</oldCode>
                <model>QTL01</model>
                <purchase_price>1.236</purchase_price>
                <currency>EUR</currency>
                <retail_price>70</retail_price>
                <retail_oldprice/>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="0"/>
                    <outlet id="86" name="Київ" instock="0"/>
                    <outlet id="87" name="Україна" instock="1"/>
                </outlets>
                <vendor>Qtap</vendor>
                <vendorCode>SD00022606</vendorCode>
            </offer>

我的任务是获得供应商 QTAP 的所有报价。所以输出将是：

<offer id="SD00022605">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_1.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_2.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16508/16508_3.jpg</picture>
                <name>Донний клапан для раковини Qtap L02 з переливом</name>
                <available>true</available>
                <oldCode>16508</oldCode>
                <model>QTL02</model>
                <purchase_price>4.635</purchase_price>
                <currency>EUR</currency>
                <retail_price>261</retail_price>
                <retail_oldprice/>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="0"/>
                    <outlet id="86" name="Київ" instock="0"/>
                    <outlet id="87" name="Україна" instock="3"/>
                </outlets>
                <vendor>Qtap</vendor>
                <vendorCode>SD00022605</vendorCode>
            </offer>
            <offer id="SD00022606">
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16509.jpg</picture>
                <picture>https://isw.b2b-sandi.com.ua/imagecache/full/1/6/16509/16509_1.jpg</picture>
                <name>Донний клапан для раковини Qtap L01 з переливом</name>
                <available>true</available>
                <oldCode>16509</oldCode>
                <model>QTL01</model>
                <purchase_price>1.236</purchase_price>
                <currency>EUR</currency>
                <retail_price>70</retail_price>
                <retail_oldprice/>
                <retail_currency>UAH</retail_currency>
                <outlets>
                    <outlet id="85" name="Харків" instock="0"/>
                    <outlet id="86" name="Київ" instock="0"/>
                    <outlet id="87" name="Україна" instock="1"/>
                </outlets>
                <vendor>Qtap</vendor>
                <vendorCode>SD00022606</vendorCode>
            </offer>

是的，问题是每次迭代都会覆盖文件的循环

Answer 1

那是因为循环中的 write() 方法每次运行时都会覆盖前一个元素。试试这样：

qtaps = etree.XML("""<offers/>""".encode())
targets = offers.xpath('//offer[./vendor/text()="Qtap"]')
for target in targets:
    qtaps.insert(-1,target)
with open('output.xml', 'wb') as doc:
    doc.write(etree.tostring(qtaps, pretty_print = True, encoding='utf-8', xml_declaration=True))

看看它是否有效。

Answer 2

因为听起来您只需要删除 XML 中的 <offer> 个节点，请考虑 XPath 的通用兄弟 XSLT，special-purpose 语言旨在转换 XML 文件。 Python 的 lxml 库可以运行 XSLT 1.0 脚本。

具体来说，身份模板和空模板可以删除所需的节点 (vendor!='Qtap')，而无需单个 for 循环。下面将保留 XML 的原始结构，减少 <offer> 个节点。

XSLT (另存为.xsl文件，一个特殊的XML文件)

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" encoding="utf-8" indent="yes"/>
    <xsl:strip-space elements="*"/>
    
    <!-- IDENTITY TRANSFORM -->
    <xsl:template match="@* | node()">
        <xsl:copy>
            <xsl:apply-templates select="@* | node()"/>
        </xsl:copy>
    </xsl:template>

    <!-- EMPTY TEMPLATE TO REMOVE CONTENT -->
    <xsl:template match="offer[vendor!='Qtap']"/>
</xsl:stylesheet>

Python

import lxml.etree as lx

# PARSE XML AND XSLT
doc = lx.parse("input.xml")
style = lx.parse("style.xsl")

# CONFIGURE AND RUN TRANSFORMER
transformer = lx.XSLT(style)
result = transformer(doc)

# OUTPUT TO FILE
result.write_output("output.xml")

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