从xml文件中提取并存储(作为csv)属性标记

Question

我正在尝试创建一个.csv文件，其中包含给定时间点的车辆数量。

    <fcd-export xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://sumo.dlr.de/xsd/fcd_file.xsd">
    <timestep time="0.00">
        <vehicle id="veh0" x="668.78" y="2768.63" angle="265.68" type="veh_passenger" speed="0.00" pos="5.10" lane="253751722#0_1" slope="0.00"/>
    </timestep>
    <timestep time="1.00">
        <vehicle id="veh0" x="666.91" y="2768.48" angle="265.68" type="veh_passenger" speed="1.88" pos="6.98" lane="253751722#0_1" slope="0.00"/>
    </timestep>
    <timestep time="2.00">
        <vehicle id="veh0" x="663.10" y="2768.20" angle="265.68" type="veh_passenger" speed="3.82" pos="10.80" lane="253751722#0_1" slope="0.00"/>
    </timestep>
    <timestep time="3.00">
        <vehicle id="veh0" x="656.86" y="2767.72" angle="265.68" type="veh_passenger" speed="6.25" pos="17.05" lane="253751722#0_1" slope="0.00"/>
    </timestep>
    <timestep time="4.00">
        <vehicle id="veh0" x="648.85" y="2767.12" angle="265.68" type="veh_passenger" speed="8.04" pos="25.09" lane="253751722#0_1" slope="0.00"/>
    </timestep>
    <timestep time="5.00">
        <vehicle id="veh0" x="639.02" y="2766.38" angle="265.68" type="veh_passenger" speed="9.85" pos="34.93" lane="253751722#0_1" slope="0.00"/>
    </timestep>
<timestep time="14.00">
        <vehicle id="veh0" x="619.10" y="2768.08" angle="85.68" type="veh_passenger" speed="8.01" pos="20.23" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="988.73" y="2991.84" angle="226.12" type="veh_passenger" speed="3.87" pos="11.45" lane="-30968089#3_0" slope="0.00"/>
    </timestep>
    <timestep time="15.00">
        <vehicle id="veh0" x="628.97" y="2768.83" angle="85.68" type="veh_passenger" speed="9.90" pos="30.13" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="984.27" y="2987.44" angle="225.26" type="veh_passenger" speed="6.25" pos="17.70" lane="-30968089#3_0" slope="0.00"/>
    </timestep>
    <timestep time="16.00">
        <vehicle id="veh0" x="640.26" y="2769.68" angle="85.68" type="veh_passenger" speed="11.32" pos="41.45" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="978.85" y="2981.98" angle="224.80" type="veh_passenger" speed="7.69" pos="25.39" lane="-30968089#3_0" slope="0.00"/>
    </timestep>
    <timestep time="14.00">
        <vehicle id="veh0" x="619.10" y="2768.08" angle="85.68" type="veh_passenger" speed="8.01" pos="20.23" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="988.73" y="2991.84" angle="226.12" type="veh_passenger" speed="3.87" pos="11.45" lane="-30968089#3_0" slope="0.00"/>
    </timestep>
    <timestep time="15.00">
        <vehicle id="veh0" x="628.97" y="2768.83" angle="85.68" type="veh_passenger" speed="9.90" pos="30.13" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="984.27" y="2987.44" angle="225.26" type="veh_passenger" speed="6.25" pos="17.70" lane="-30968089#3_0" slope="0.00"/>
    </timestep>
    <timestep time="16.00">
        <vehicle id="veh0" x="640.26" y="2769.68" angle="85.68" type="veh_passenger" speed="11.32" pos="41.45" lane="-253751722#0_1" slope="0.00"/>
        <vehicle id="veh1" x="978.85" y="2981.98" angle="224.80" type="veh_passenger" speed="7.69" pos="25.39" lane="-30968089#3_0" slope="0.00"/>
    </timestep>

这就是我到目前为止所做的：

      import xml.etree.ElementTree as ET
      xml_tree = ET.parse("trace.xml")
      root = xml_tree.getroot()
      while i<150:
          print(root[i][1].get('id'))
          i=i+1

我尝试使用以下命令索引标签：root[x][0].get('id')这里x表示时间。但是当存在多个车辆标记时，它只返回python中相对较新的一个attributes.Im，任何帮助都将是appreciated.Thanks

Answer 1

对于这种类型的作业，最好使用带有lxml的xpath：

from lxml import etree
vehicles = """[your xml]"""
doc = etree.XML(vehicles.encode())
for ts in doc.xpath('//timestep'):
    print('time: ',ts.attrib['time'])
    for vehicle in ts.xpath('./vehicle/@id'):
        print('\tvehicle id:',vehicle)

输出：

.....
time:  4.00
    vehicle id: veh0
time:  5.00
    vehicle id: veh0
time:  14.00
    vehicle id: veh0
    vehicle id: veh1
time:  15.00
    vehicle id: veh0
    vehicle id: veh1
.....