如何在python中使用xpath查询具有名称空间的xml数据

我尝试使用以下代码对具有名称空间的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)

从lxml导入etree
从io导入StringIO
xml=“”
2015-07-07T15:16:40Z
某个名字
2261.8
2015-07-07T15:30:42Z
2261.6
2015-07-07T15:30:43Z
2262
2015-07-07T15:30:46Z
2261.8
2015-07-07T15:30:47Z
'''
#这是为了模拟上述xml是从文件中读取的
file=StringIO（unicode（xml））#对于python3，使用“file=StringIO（xml）”
#从文件中读取xml
tree=etree.parse（文件）
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'
对于tree.xpath（expr，namespaces=ns）中的元素：
打印（element.text）

我希望代码有以下输出：

2261.8
2261.6
2262.0
2261.8

替换XML根元素时

<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">

与

代码正在运行

---

您对如何使其与名称空间一起工作有何建议？

您可以将名称空间定义为-

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'}

这将定义

的前缀http://www.topografix.com/GPX/1/1“

作为

n

，然后在XPath查询中，可以使用该前缀。范例-

expr = 'n:trk/n:trkseg/n:trkpt/n:ele'

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

这是因为根节点的xmlns是-

'http://www.topografix.com/GPX/1/1“

-因此，除非子节点使用不同的前缀或指定自己的名称空间，否则所有子节点都会自动将其作为xmlns（名称空间）继承

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

---

这意味着我把xpath查询搞砸了。不是使用<代码> ExpR= Trk/TrkSEG/TrkPt/ELE’< /代码>我应该使用<代码> ExpR= 'xMLNs:Trk/XMLN:TrkSEG/XMLN:TrkPt/XMLN:ELE’< /Cord>来考虑“空白”命名空间。有人能帮助我吗？请

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