在python中如何使用xpath查询具有名称空间的xml数据

2024-03-29 14:27:30 发布

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我尝试使用以下代码对具有命名空间的XML数据应用XPath查询:

from lxml import etree
from io import StringIO

xml = '''
<gpx creator="udos" version="1.1" xmlns="http://www.topografix.com/GPX/1/1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd http://www.garmin.com/xmlschemas/GpxExtensions/v3 http://www.garmin.com/xmlschemas/GpxExtensionsv3.xsd http://www.garmin.com/xmlschemas/TrackPointExtension/v1 http://www.garmin.com/xmlschemas/TrackPointExtensionv1.xsd" xmlns:gpxtpx="http://www.garmin.com/xmlschemas/TrackPointExtension/v1" xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3">
 <metadata>
  <time>2015-07-07T15:16:40Z</time>
 </metadata>
 <trk>
  <name>some name</name>
  <trkseg>
   <trkpt lat="46.3884140" lon="10.0286290">
    <ele>2261.8</ele>
    <time>2015-07-07T15:30:42Z</time>
   </trkpt>
   <trkpt lat="46.3884050" lon="10.0286240">
    <ele>2261.6</ele>
    <time>2015-07-07T15:30:43Z</time>
   </trkpt>
   <trkpt lat="46.3884000" lon="10.0286210">
    <ele>2262.0</ele>
    <time>2015-07-07T15:30:46Z</time>
   </trkpt>
   <trkpt lat="46.3884000" lon="10.0286210">
    <ele>2261.8</ele>
    <time>2015-07-07T15:30:47Z</time>
   </trkpt>
  </trkseg>
 </trk>
</gpx>
'''

# this is to simulate that above xml was read from a file
file = StringIO(unicode(xml))   # with python 3 use "file = StringIO(xml)"

# reading the xml from a file
tree = etree.parse(file)

ns = {'xmlns': 'http://www.topografix.com/GPX/1/1',
      'xmlns:xsi': 'http://www.w3.org/2001/XMLSchema-instance',
      'xmlns:gpxtpx': 'http://www.garmin.com/xmlschemas/TrackPointExtension/v1',
      'xmlns:gpxx': 'http://www.garmin.com/xmlschemas/GpxExtensions/v3'}

expr = 'trk/trkseg/trkpt/ele'

for element in tree.xpath(expr, namespaces=ns):
    print(element.text)

我期望从代码中得到以下输出:

2261.8
2261.6
2262.0
2261.8

当您替换XML根元素时

^{pr2}$

<gpx>

代码正在工作。。。在

有什么建议可以让它和名称空间一起工作吗?在


Tags: fromcomhttptimewwwxmlgpxfile
1条回答
网友
1楼 · 发布于 2024-03-29 14:27:30

您可以将命名空间定义为-

ns = {'n': 'http://www.topografix.com/GPX/1/1',
      'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
      'gpxtpx': 'http://www.garmin.com/xmlschemas/TrackPointExtension/v1',
      'gpxx': 'http://www.garmin.com/xmlschemas/GpxExtensions/v3'}

这将把'http://www.topografix.com/GPX/1/1'的前缀定义为n,然后在XPath查询中,可以使用该前缀。示例-

^{pr2}$

这是因为根节点的xmlns是-'http://www.topografix.com/GPX/1/1'-因此所有子节点都会自动将其作为xmlns(名称空间)继承,除非子节点使用不同的前缀或指定自己的名称空间。在

示例/演示-

In [44]: ns = {'n': 'http://www.topografix.com/GPX/1/1',
   ....:       'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
   ....:       'gpxtpx': 'http://www.garmin.com/xmlschemas/TrackPointExtension/v1',
   ....:       'gpxx': 'http://www.garmin.com/xmlschemas/GpxExtensions/v3'}

In [45]:

In [45]: expr = 'n:trk/n:trkseg/n:trkpt/n:ele'

In [46]: for element in tree.xpath(expr, namespaces=ns):
   ....:         print(element.text)
   ....:
2261.8
2261.6
2262.0
2261.8

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