Read GPX using Python ElementTree.register_namespace?

问题:

I have been beating my head against the wall for some time now. According to the documentation, this should be simple. All I want to do is read a GPX file. However, GPX files liberally use namespaces, which theoretically make sense. I cannot seem to get ElementTree to read them, though. Here is the code I am trying to use...

def loadGpx(self, sourceFile):     ElementTree.register_namespace('gpx', 'http://www.topografix.com/GPX/1/1')     eTree = ElementTree.ElementTree()     eTree.parse(sourceFile)      print eTree.findall('wpt') 

To pull out waypoints from a GPX file like this...

<?xml version="1.0" encoding="utf-8"?> <gpx creator="Garmin Desktop App" version="1.1"      xsi:schemaLocation="http://www.topografix.com/GPX/1/1                      http://www.topografix.com/GPX/1/1/gpx.xsd                      http://www.garmin.com/xmlschemas/WaypointExtension/v1                      http://www8.garmin.com/xmlschemas/WaypointExtensionv1.xsd                      http://www.garmin.com/xmlschemas/TrackPointExtension/v1                      http://www.garmin.com/xmlschemas/TrackPointExtensionv1.xsd                      http://www.garmin.com/xmlschemas/GpxExtensions/v3                      http://www8.garmin.com/xmlschemas/GpxExtensionsv3.xsd                      http://www.garmin.com/xmlschemas/ActivityExtension/v1                      http://www8.garmin.com/xmlschemas/ActivityExtensionv1.xsd                      http://www.garmin.com/xmlschemas/AdventuresExtensions/v1                      http://www8.garmin.com/xmlschemas/AdventuresExtensionv1.xsd"      xmlns="http://www.topografix.com/GPX/1/1"      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"      xmlns:wptx1="http://www.garmin.com/xmlschemas/WaypointExtension/v1"      xmlns:gpxtrx="http://www.garmin.com/xmlschemas/GpxExtensions/v3"      xmlns:gpxtpx="http://www.garmin.com/xmlschemas/TrackPointExtension/v1"      xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3"      xmlns:abp="http://www.garmin.com/xmlschemas/ActivityExtension/v1"      xmlns:adv="http://www.garmin.com/xmlschemas/AdventuresExtensions/v1">      <metadata>         <link href="http://www.garmin.com">           <text>Garmin International</text>         </link>         <time>2012-01-17T03:21:12Z</time>         <bounds maxlat="45.708811283111572" maxlon="-121.3884991966188"                  minlat="45.407062936574221" minlon="-121.54939779080451" />     </metadata>    <wpt lat="45.708682453259826" lon="-121.51224257424474">     <time>2012-01-06T19:00:02Z</time>     <name>1-State and First, start MHL</name>     <sym>Bike Trail</sym>     <extensions>       <gpxx:WaypointExtension>         <gpxx:DisplayMode>SymbolAndName</gpxx:DisplayMode>       </gpxx:WaypointExtension>     </extensions>   </wpt>    <wpt lat="45.615267734974623" lon="-121.43857721239328">     <time>2012-01-07T15:38:14Z</time>     <name>10-Right at fork staying on Huskey Rd</name>     <sym>Bike Trail</sym>     <extensions>       <gpxx:WaypointExtension>         <gpxx:DisplayMode>SymbolAndName</gpxx:DisplayMode>       </gpxx:WaypointExtension>     </extensions>   </wpt> 

True, it will take more than just print eTree.findall('wpt'), but if I can get that far, I have worked with xml before. That part is easy. This namespace thing though, is driving me nuts.

I thank you in advance. This is driving me nuts.

回答1:

register_namespace() controls the prefixes used when serializing XML, but it does not affect parsing.

With ElementTree, do it like this:

from xml.etree import ElementTree as ET  tree = ET.parse("gpx.xml") for elem in tree.findall("{http://www.topografix.com/GPX/1/1}wpt"):     print elem 

Resulting output:

<Element '{http://www.topografix.com/GPX/1/1}wpt' at 0x201c550> <Element '{http://www.topografix.com/GPX/1/1}wpt' at 0x201c730> 

With lxml, you can also use this:

from lxml import etree  NSMAP = {"gpx": "http://www.topografix.com/GPX/1/1"}  tree = etree.parse("gpx.xml") for elem in tree.findall("gpx:wpt", namespaces=NSMAP):     print elem 

回答2:

Why don't you just use an existing GPX library?

shameless plug: With gpxpy https://github.com/tkrajina/gpxpy parsing waypoints from your file works perfectly:

import gpxpy  gpx_sample = """...your GPX sample here..."""  gpx = gpxpy.parse(gpx_sample)  for wpt in gpx.waypoints:     print wpt.latitude, wpt.longitude 

Even if you don't want to use the library you can just check the code to see how it parses the XML file.

文章来源: Read GPX using Python ElementTree.register_namespace?