如何处理具有相同标签的 XML 元素迭代嵌套属性答案

【问题标题】：How to handle XML element iter nested attributes with the same tag如何处理具有相同标签的 XML 元素迭代嵌套属性
【发布时间】：2021-06-11 09:59:24
【问题描述】：

我正在尝试解析 NPORT-P XML SEC 提交。我的代码（Python 3.6.8）带有示例 XML 记录：

import xml.etree.ElementTree as ET
content_xml = '<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/nport" xmlns:com="http://www.sec.gov/edgar/common" xmlns:ncom="http://www.sec.gov/edgar/nportcommon" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><headerData></headerData><formData><genInfo></genInfo><fundInfo></fundInfo><invstOrSecs><invstOrSec><name>N/A</name><lei>N/A</lei><title>US 10YR NOTE (CBT)Sep20</title><cusip>N/A</cusip>        <identifiers>          <ticker value="TYU0"/>        </identifiers>        <derivativeInfo>          <futrDeriv derivCat="FUT">            <counterparties>              <counterpartyName>Chicago Board of Trade</counterpartyName>              <counterpartyLei>549300EX04Q2QBFQTQ27</counterpartyLei>            </counterparties><payOffProf>Short</payOffProf>            <descRefInstrmnt>              <otherRefInst>                <issuerName>U.S. Treasury 10 Year Notes</issuerName>                <issueTitle>U.S. Treasury 10 Year Notes</issueTitle>                <identifiers>                  <cusip value="N/A"/><other otherDesc="USER DEFINED" value="TY_Comdty"/>                </identifiers>              </otherRefInst>            </descRefInstrmnt>            <expDate>2020-09-21</expDate>            <notionalAmt>-2770555</notionalAmt>            <curCd>USD</curCd>            <unrealizedAppr>-12882.5</unrealizedAppr></futrDeriv>        </derivativeInfo>      </invstOrSec>    </invstOrSecs>    <signature>    </signature>  </formData></edgarSubmission>'
content_tree = ET.ElementTree(ET.fromstring(bytes(content_xml, encoding='utf-8')))
content_root = content_tree.getroot()
for edgar_submission in content_root.iter('{http://www.sec.gov/edgar/nport}edgarSubmission'):

    for form_data in edgar_submission.iter('{http://www.sec.gov/edgar/nport}formData'):

        for genInfo in form_data.iter('{http://www.sec.gov/edgar/nport}genInfo'):
            None
        for fundInfo in form_data.iter('{http://www.sec.gov/edgar/nport}fundInfo'):
            None            
        for invstOrSecs in form_data.iter('{http://www.sec.gov/edgar/nport}invstOrSecs'):

            for invstOrSec in invstOrSecs.iter('{http://www.sec.gov/edgar/nport}invstOrSec'):

                myrow = []
                myrow.append(getattr(invstOrSec.find('{http://www.sec.gov/edgar/nport}name'), 'text', ''))
                myrow.append(getattr(invstOrSec.find('{http://www.sec.gov/edgar/nport}lei'), 'text', ''))
                security_title = getattr(invstOrSec.find('{http://www.sec.gov/edgar/nport}title'), 'text', '')
                myrow.append(security_title)
                myrow.append(getattr(invstOrSec.find('{http://www.sec.gov/edgar/nport}cusip'), 'text', ''))

                for identifiers in invstOrSec.iter('{http://www.sec.gov/edgar/nport}identifiers'):

                    if identifiers.find('{http://www.sec.gov/edgar/nport}isin') is not None:
                        myrow.append(identifiers.find('{http://www.sec.gov/edgar/nport}isin').attrib['value'])
                    else:
                        myrow.append('')
                        if security_title == "US 10YR NOTE (CBT)Sep20":
                            print("No ISIN")

                    if identifiers.find('{http://www.sec.gov/edgar/nport}ticker') is not None:
                        myrow.append(identifiers.find('{http://www.sec.gov/edgar/nport}ticker').attrib['value'])
                    else:
                        myrow.append('')
                        if security_title == "US 10YR NOTE (CBT)Sep20":
                            print("No Ticker")

                    if identifiers.find('{http://www.sec.gov/edgar/nport}other') is not None:
                        myrow.append(identifiers.find('{http://www.sec.gov/edgar/nport}other').attrib['value'])
                    else:
                        myrow.append('')
                        if security_title == "US 10YR NOTE (CBT)Sep20":
                            print("No Other")

这段代码的输出是：

No ISIN
No Other
No ISIN
No Ticker

除了标识符 iter invstOrSec.iter('{http://www.sec.gov/edgar/nport}identifiers') 在 formData>invstOrSecs>invstOrSec 下找到标识符以及在下的其他标识符之外，这工作正常formData>invstOrSecs>invstOrSec>derivativeInfo>futrDeriv>descRefInstrmnt>otherRefInst 下的嵌套标记。如何将我的 iter 或 find 限制在正确的级别？我没有成功尝试获取父级，但我没有找到如何使用 {namespace} 标记符号来执行此操作。有什么想法吗？

【问题讨论】：

想要的输出到底是什么？
ElementTree 中的元素没有对父元素的任何引用。但是在 lxml 库中，有一个getparent() 方法。 lxml.de/tutorial.html#elements-are-lists
输出应该是：No ISIN No Other

标签： python xml namespaces find elementtree

【解决方案1】：

所以我使用这样的导入从 ElementTree 切换到 lxml 以避免代码更改：

from lxml import etree as ET

请务必检查https://lxml.de/1.3/compatibility.html 以避免出现兼容性问题。在我的情况下，lxml 没有问题。

然后我可以使用 getparent() 方法来仅读取 XML 文件右侧部分的标识符：

if identifiers.getparent().tag == '{http://www.sec.gov/edgar/nport}invstOrSec':

【讨论】：