How can I grab data series from xml or tcx file

Question

I want to treat data from .tcx file (xml form) between specific tags with Python.
File format is like as follows.

 <Track>
      <Trackpoint>
        <Time>2015-08-29T22:04:39.000Z</Time>
        <Position>
          <LatitudeDegrees>37.198049426078796</LatitudeDegrees>
          <LongitudeDegrees>127.07204628735781</LongitudeDegrees>
        </Position>
        <AltitudeMeters>34.79999923706055</AltitudeMeters>
        <DistanceMeters>7.309999942779541</DistanceMeters>
        <HeartRateBpm>
          <Value>102</Value>
        </HeartRateBpm>
        <Cadence>76</Cadence>
        <Extensions>
          <TPX xmlns="http://www.garmin.com/xmlschemas/ActivityExtension/v2">
            <Watts>112</Watts>
          </TPX>
        </Extensions>
      </Trackpoint>
....Lots of <Trackpoint> ... </Trackpoint>
</Track>

Eventually, I'll make Data table with columns of 'Lattitude, Altitude, ... Watts'.
First I tried to make a list from taged data (like Watts ... /Watts) with BeautifulSoup, xpath etc. But I'm a newbie to deal with these tools. How can I grab data between tags in xml file with Python?

Answer 1

You could use the lxml module, along with XPath. lxml is good for parsing XML/HTML, traversing element trees and returning element text/attributes. You can select particular elements, sets of elements or attributes of elements using XPath. Using your example data:

content = '''
<Track>
      <Trackpoint>
        <Time>2015-08-29T22:04:39.000Z</Time>
        <Position>
          <LatitudeDegrees>37.198049426078796</LatitudeDegrees>
          <LongitudeDegrees>127.07204628735781</LongitudeDegrees>
        </Position>
        <AltitudeMeters>34.79999923706055</AltitudeMeters>
        <DistanceMeters>7.309999942779541</DistanceMeters>
        <HeartRateBpm>
          <Value>102</Value>
        </HeartRateBpm>
        <Cadence>76</Cadence>
        <Extensions>
          <TPX xmlns="http://www.garmin.com/xmlschemas/ActivityExtension/v2">
            <Watts>112</Watts>
          </TPX>
        </Extensions>
      </Trackpoint>
....Lots of <Trackpoint> ... </Trackpoint>
</Track>
'''

from lxml import etree

tree = etree.XML(content)
time = tree.xpath('Trackpoint/Time/text()')

print(time)

Output

['2015-08-29T22:04:39.000Z']