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我正在尝试复制本教程中的示例，但将 iterparse 与 elem.clear() 一起使用。

XML 示例：

<?xml version="1.0" encoding="UTF-8"?>
<scenario>
    <world>
        <region name="USA">
            <AgSupplySector name="Corn" nocreate="1">
                <AgSupplySubsector name="Corn_NelsonR" nocreate="1">
                    <AgProductionTechnology name="Corn_NelsonR" nocreate="1">
                        <period year="1975">
                            <Non-CO2 name="SO2_1_AWB">
                                <input-emissions>3.98749e-05</input-emissions>
                                <output-driver/>
                                <gdp-control name="GDP_control">
                                    <max-reduction>60</max-reduction>
                                    <steepness>3.5</steepness>
                                </gdp-control>
                            </Non-CO2>
                            <Non-CO2 name="NOx_AWB">
                                <input-emissions>0.000285263</input-emissions>
                                <output-driver/>
                                <gdp-control name="GDP_control">
                                    <max-reduction>60</max-reduction>
                                    <steepness>3.5</steepness>
                                </gdp-control>
                            </Non-CO2>
                        </period>
                    </AgProductionTechnology>
                </AgSupplySubsector>
            </AgSupplySector>
        </region>
    </world>
</scenario>

预期的输出是这样的： 桌子 我正在尝试使用以下代码对其进行解析：

import os
import xml.etree.cElementTree as etree
import codecs
import csv

PATH = 'D:\Book1'
FILENAME_BIO = 'Test.csv'
FILENAME_XML = 'all_aglu_emissions.xml'
ENCODING = "utf-8"


pathBIO = os.path.join(PATH, FILENAME_BIO)
pathXML = os.path.join(PATH, FILENAME_XML)

with codecs.open(pathBIO, "w", ENCODING) as bioFH:
    bioWriter = csv.writer(bioFH, quoting=csv.QUOTE_MINIMAL)
    bioWriter.writerow(['Year','Gas', 'Value','Technology','Crop','Country'])

    for event, elem in etree.iterparse(pathXML, events=('start','end')):
        if event == 'start' and elem.tag == 'region':
            str1 = elem.attrib['name']
        elif event == 'start' and elem.tag == 'AgSupplySector':
            str2 = elem.attrib['name']
        elif event == 'start' and elem.tag == 'AgProductionTechnology':
            str3 = elem.attrib['name']
        elif event == 'start' and elem.tag == 'period':
            str4 = elem.attrib['year']
        elif event == 'start' and elem.tag == 'Non-CO2':
            str5 = elem.attrib['name']
        elif event == 'end' and elem.tag == 'input-emissions':
            for em in elem.iter('input-emissions'):
                str6 = em.text
                bioWriter.writerow([str4, str5, str6, str3, str2, str1])
            
            elem.clear()

我的问题是我得到了更多额外的行，其中 str6 为空字段。可能，我在这里有嵌套问题。请帮忙。错误示例（出现 0 个字段）： 在此处输入图像描述

4

1 回答 1

1

for em in elem.iter('input-emissions')循环没用，放弃吧。

import os
import xml.etree.ElementTree as etree
import csv

PATH = '.'
FILENAME_BIO = 'Test.csv'
FILENAME_XML = 'all_aglu_emissions.xml'


pathBIO = os.path.join(PATH, FILENAME_BIO)
pathXML = os.path.join(PATH, FILENAME_XML)

with open(pathBIO, 'w', encoding='utf8', newline='') as bioFH:
    bioWriter = csv.writer(bioFH, quoting=csv.QUOTE_MINIMAL)
    bioWriter.writerow('Year Gas Value Technology Crop Country'.split())

    for event, elem in etree.iterparse(pathXML, events=('start',)):
        if elem.tag == 'region':
            str1 = elem.attrib['name']
        elif elem.tag == 'AgSupplySector':
            str2 = elem.attrib['name']
        elif elem.tag == 'AgProductionTechnology':
            str3 = elem.attrib['name']
        elif elem.tag == 'period':
            str4 = elem.attrib['year']
        elif elem.tag == 'Non-CO2':
            str5 = elem.attrib['name']
        elif elem.tag == 'input-emissions':
            str6 = elem.text
            bioWriter.writerow([str4, str5, str6, str3, str2, str1])
        elem.clear()

我对代码做了一些其他细微的更改，因为我假设您为此使用 Python 3。它们包括 usingxml.etree.ElementTree而不是 obsolete xml.etree.cElementTree，跳过codecs模块（Python 3 可以本地执行此操作）并将newline=''参数传递给open()调用，因此csv模块可以自己正确处理换行符。

由于收听start事件足以达到预期的效果，因此我end完全放弃了处理该事件。

结果是

年份、天然气、价值、技术、作物、国家
1975,SO2_1_AWB,3.98749e-05,Corn_NelsonR,Corn,USA
1975,NOx_AWB,0.000285263,Corn_NelsonR,Corn,USA
于 2021-06-07T17:51:10.393 回答