使用Python中的条件更新XML节点值

Question

在下面的XML中，我想解析它，并将“PolicyId”的值更新为一些随机值，例如“POL111112NGJ”和“TransactionDate”，仅当它满足条件PolicyId==pol00002ngj时，才更新为当前日期和时间。下面我给出的代码更新了“PolicyId和TransactionDate”的所有值，我只想在条件为TRUE时更新该值。根据给定的XML，我希望将前3个集合更新为相同的“PolicyId和TransactionDate”值。第四个设置为不同的值

我尝试添加条件~~如果ROW.attrib['PolicyId']='POL000002NGJ'：~~我得到“keyrerror:'PolicyId'”

有人能帮我弄明白怎么处理吗

--BEFORE UPDATING---

<TABLE>
   <ROW>
      <PolicyId>POL000002NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL000002NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL111111NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
</TABLE>


--AFTER UPDATING---

<TABLE>
   <ROW>
      <PolicyId>POL545678NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>2020-03-27T10:56:15.00</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL545678NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3A2</BusinessCoverageCode>
      <TransactionDate>2020-03-27T10:56:15.00</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL111111NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
</TABLE>

我正在使用的代码

import xml.etree.ElementTree as ET
from datetime import datetime, timedelta
import random, string

class TimestampUpdater(object):

    def __init__(self, filepath):
        self.meta_file = filepath
        self.tree = ET.parse(r'C:\Users\\XML\python.xml')

    def getMetadataTree(self):
        return self.tree

    def getMetadataRoot(self):
        return self.tree.getroot()
    
    def updatepolicyid(self):
        for ROW in self.getMetadataRoot().findall('ROW'): ##    
            PolicyId = ROW.find('PolicyId')
            
            if ROW.attrib['PolicyId'] == 'POL702965NGJ':
                
                x = 'POL' + ''.join(random.choices(string.digits, k=6)) + 'NGJ'
                PolicyId.text = x
            #PolicyId.set('updated', 'yes')
            self.getMetadataTree().write(self.meta_file)
                   
    
    def updateLastModified(self):
            today = datetime.now()
            for ROW in self.getMetadataRoot().findall('ROW'): ##
                TransactionDate = ROW.find('TransactionDate')
                previous_update = datetime.strptime(TransactionDate.text, '%Y-%m-%dT%H:%M:%S.%f')
                if previous_update < today:
                    TransactionDate.text = today.strftime('%Y-%m-%dT%H:%M:%S.%f')
                    self.getMetadataTree().write(self.meta_file)
                    
                    

def print_file_content(filename):
    """Print contents of a file"""
    with open(filename, 'r') as fh:
        for line in fh:
            print(line.rstrip())

if __name__ == '__main__':
    metafile = 'output.xml'
    print("\n====Before updating:====")
    print_file_content(metafile)
    updater = TimestampUpdater(metafile)
    updater.updateLastModified()
    updater.updatepolicyid() 
    print("\n====After updating:====")
    print_file_content(metafile)

Answer 1

下面的代码使用python ElementTree XML库。（不使用外部库）

它使用xpath并查找具有特定PolicyId值的行

它将日期更新为当前日期

import xml.etree.ElementTree as ET

import datetime

xml = '''<TABLE>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL111111NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
</TABLE>
'''

root = ET.fromstring(xml)
rows_to_update = root.findall(".//ROW/[PolicyId='POL111111NGJ']")
for row in rows_to_update:
    row.find('TransactionDate').text = str(datetime.datetime.now())
ET.dump(root)

Answer 2

这里有一个相对简单的解决方案，但它使用lxml而不是xml.etree.ElementTree。为了简单起见，我只专注于更改节点值；显然，您必须采用它来满足其他需求

policy = """[your xml above]""" #if parsing from an xml string
from lxml import etree

doc = etree.XML(policy.encode()) #if parsing from an xml string
doc = etree.parse(r'path\to\your\file\policy.xml') #if parsing from a file
replacements = ["some random policy number","some random date"]

targets = doc.xpath('//ROW[PolicyId="POL000002NGJ"]')
for target in targets:
    target.xpath('./PolicyId')[0].text = replacements[0]
    target.xpath('.//TransactionDate')[0].text = replacements[1]
print(etree.tostring(doc).decode())
# or to save to a new file:
doc.write('new_policy.xml', pretty_print=True, xml_declaration=True,   encoding="utf-8")

输出：

<TABLE>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X1</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>some random number</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>some random date</TransactionDate>
   </ROW>
   <ROW>
      <PolicyId>POL111111NGJ</PolicyId>
      <BusinessCoverageCode>COV00002D3X4</BusinessCoverageCode>
      <TransactionDate>2020-03-23T10:56:15.00</TransactionDate>
   </ROW>
</TABLE>