将Python与bs4（Lxml）结合使用，在XML标签内编辑文本

Question

I am new to both python, BS4 and the Lxml parser.

I am trying to delete the final three characters from an XML postcode tag to anonymise data.

The current code runs fine without any errors yet the last three digits are not deleted from the outputted XML file.

XML MOCK data -

<?xml version="1.0" encoding="UTF-8"?>
<!-- Please note that this file is properly formed, and serves as an example of a file that will load into the ILR DC system.  The data is anonymised and does not refer to a real-world provider, learning delivery or learner.  Based on the ILR specification, version 2, dated April 2018-->
<Message xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="ESFA/ILR/2018-19" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="ESFA/ILR/2018-19">
    <Header>
        <CollectionDetails>
            <Collection>ILR</Collection>
            <Year>1819</Year>
            <FilePreparationDate>2018-01-07</FilePreparationDate>
        </CollectionDetails>
        <Source>
            <ProtectiveMarking>OFFICIAL-SENSITIVE-Personal</ProtectiveMarking>
            <UKPRN>99999999</UKPRN>
            <SoftwareSupplier>SupplierName</SoftwareSupplier>
            <SoftwarePackage>SystemName</SoftwarePackage>
            <Release>1</Release>
            <SerialNo>01</SerialNo>
            <DateTime>2018-06-26T11:14:05</DateTime>
            <!-- This and the next element only appear in files generated by FIS -->
            <ReferenceData>Version5.0, LARS 2017-08-01</ReferenceData>
            <ComponentSetVersion>1</ComponentSetVersion>
        </Source>
    </Header>
    <SourceFiles>
        <!-- The SourceFiles group only appears in files generated by FIS -->
        <SourceFile>
            <SourceFileName>ILR-LLLLLLLL1819-20180626-144401-01.xml</SourceFileName>
            <FilePreparationDate>2018-06-26</FilePreparationDate>
            <SoftwareSupplier>Software Systems Inc.</SoftwareSupplier>
            <SoftwarePackage>GreatStuffMIS</SoftwarePackage>
            <Release>1</Release>
            <SerialNo>01</SerialNo>
            <DateTime>2018-06-26T11:14:05</DateTime>
        </SourceFile>
    </SourceFiles>
    <LearningProvider>
        <UKPRN>99999999</UKPRN>
    </LearningProvider>
    <!-- 16 yr old learner undertaking full time 16-19 (excluding apprenticeships) funded programme -->
    <Learner>
        <LearnRefNumber>16Learner</LearnRefNumber>
        <PMUKPRN>87654321</PMUKPRN>
        <CampId>1234ABCD</CampId>
        <ULN>1061484016</ULN>
        <FamilyName>Smith</FamilyName>
        <GivenNames>Jane</GivenNames>
        <DateOfBirth>1999-02-27</DateOfBirth>
        <Ethnicity>31</Ethnicity>
        <Sex>F</Sex>
        <LLDDHealthProb>2</LLDDHealthProb>
        <Accom>5</Accom>
        <PlanLearnHours>440</PlanLearnHours>
        <PlanEEPHours>100</PlanEEPHours>
        <MathGrade>NONE</MathGrade>
        <EngGrade>D</EngGrade>
        <PostcodePrior>BR1 7SS</PostcodePrior>
        <Postcode>BR1 7SS</Postcode>
        <AddLine1>The Street</AddLine1>
        <AddLine2>ToyTown</AddLine2>
        <LearnerFAM>
            <LearnFAMType>LSR</LearnFAMType>
            <LearnFAMCode>55</LearnFAMCode>
        </LearnerFAM>
        <LearnerFAM>
            <LearnFAMType>EDF</LearnFAMType>
            <LearnFAMCode>2</LearnFAMCode>
        </LearnerFAM>
        <LearnerFAM>
            <LearnFAMType>MCF</LearnFAMType>
            <LearnFAMCode>3</LearnFAMCode>
        </LearnerFAM>
        <LearnerFAM>
            <LearnFAMType>FME</LearnFAMType>
            <LearnFAMCode>2</LearnFAMCode>
        </LearnerFAM>
        <LearnerFAM>
            <LearnFAMType>PPE</LearnFAMType>
            <LearnFAMCode>2</LearnFAMCode>
        </LearnerFAM>

Current Code :

#Importing BS4# 
from bs4 import BeautifulSoup

#Opening Origional XML File, Setting soup to BS# 
with open("ILR_mock_data.xml", "r") as infile:
    xml_text = infile.read()

soup = BeautifulSoup(xml_text, 'xml')




#Postcode (Deleting last 3 digits)#
for postcode_tag in soup.find_all("Postcode"):
    postcode_tag.string[:-3]


with open("SEND_ME_TO_RCU.xml", "w") as outfile:
    outfile.write(soup.prettify())

Hopefully where XML has

<Postcode>BR1 7SS</Postcode>

The new postcode will be

<Postcode>BR1</Postcode>

Answer 1

Fixed the problem using

for pripostcode_tag in soup.find_all("PostcodePrior"):   
    pripostcode_tag.string = pripostcode_tag.string[:-3]

Answer 2

The code below uses a simplified version of the xml ( but should work with the OP's xml as well ). It does not make any use of an external library.

import xml.etree.ElementTree as ET

xml_sample = '''<r><Postcode>ACBDEF</Postcode></r>'''
root = ET.fromstring(xml_sample)
post_codes = root.findall('.//Postcode')
for pc in post_codes:
  pc.text = pc.text[:-3]
ET.dump(root)

output

<r><Postcode>ACB</Postcode></r>