Plot variables from XML file in python

Question

I have and XML file (please see attached).

I made a python script to try to obtain information from the XML to later do some plots.

The aim of this code is:

a. To iterate over the XML file to find the </event> and then </origin> and then <quality> to reach <azimuthalGap>348.000</azimuthalGap>

b. To save each azimutalGap in the gaps=[] variable

c. To plot an Histograms of azimutalGap.

So far I tried the code:

import xml.etree.ElementTree as ET

def parse_azimuthal_gaps(xml_file):
    gaps = []

    # Parse the XML file
    tree = ET.parse(xml_file)
    root = tree.getroot()

    # Iterate through each event
    for event in root.findall(".//event"):
        origin = event.find(".//origin")
        if origin is not None:
            # Find the azimuthal gap (if present)
            azimuthal_gap = origin.find(".//quality/azimuthalGap")
            if azimuthal_gap is not None:
                gap_value = azimuthal_gap.text
                if gap_value is not None:
                    try:
                        gaps.append(float(gap_value))
                    except ValueError:
                        continue  # Skip if not a valid float

    return gaps

# Parse azimuthal gaps from the ISC XML file
gaps = parse_azimuthal_gaps("SCB_earthquakes.xml")
print("Azimuthal Gaps:", gaps[:10])  # Print the first 10 gaps for inspection

But I always get empty gaps varible.

The input file has this format:

</event>
<event publicID="smi:ISC/evid=602401243">
  <preferredOriginID>smi:ISC/origid=601808754</preferredOriginID>
  <description>
    <text>Peru-Bolivia border region</text>
    <type>Flinn-Engdahl region</type>
  </description>
  <type>earthquake</type>
  <typeCertainty>known</typeCertainty>
  <comment>
    <text>Event reviewed by the ISC</text>
  </comment>
  <creationInfo>
    <agencyID>ISC</agencyID>
    <author>ISC</author>
  </creationInfo>
  <origin publicID="smi:ISC/origid=601808754">
    <time>
      <value>2011-01-23T09:13:37.30Z</value>
      <uncertainty>0.96</uncertainty>
    </time>
    <latitude>
      <value>-11.9240</value>
    </latitude>
    <longitude>
      <value>-68.9133</value>
    </longitude>
    <depth>
      <value>58000.0</value>
    </depth>
    <depthType>operator assigned</depthType>
    <quality>
      <usedPhaseCount>8</usedPhaseCount>
      <associatedStationCount>6</associatedStationCount>
      <standardError>0.4800</standardError>
      <azimuthalGap>353.000</azimuthalGap>
      <minimumDistance>4.260</minimumDistance>
      <maximumDistance>5.070</maximumDistance>
    </quality>
    <creationInfo>
      <author>SCB</author>
      <agencyID>SCB</agencyID>
    </creationInfo>
    <originUncertainty>
      <preferredDescription>uncertainty ellipse</preferredDescription>
      <minHorizontalUncertainty>20399.9996185303</minHorizontalUncertainty>
      <maxHorizontalUncertainty>96000</maxHorizontalUncertainty>
      <azimuthMaxHorizontalUncertainty>83.0</azimuthMaxHorizontalUncertainty>
    </originUncertainty>
    <arrival publicID="smi:ISC/pickid=637614753/hypid=601808754">
      <pickID>smi:ISC/pickid=637614753</pickID>
      <phase>Pn</phase>
      <azimuth>170.165</azimuth>
      <distance>4.404</distance>
      <timeResidual>3.6</timeResidual>
    </arrival>
    <arrival publicID="smi:ISC/pickid=637614754/hypid=601808754">
      <pickID>smi:ISC/pickid=637614754</pickID>
      <phase>Sn</phase>
      <azimuth>170.165</azimuth>
      <distance>4.404</distance>
      <timeResidual>4.6</timeResidual>
    </arrival>
  </origin>
  <pick publicID="smi:ISC/pickid=637614753">
    <time>
      <value>2011-01-23T09:14:46.10Z</value>
    </time>
    <waveformID networkCode="IR" stationCode="LPAZ"></waveformID>
    <onset>impulsive</onset>
    <polarity>positive</polarity>
    <phaseHint>Pn</phaseHint>
  </pick>
  <pick publicID="smi:ISC/pickid=637614754">
    <time>
      <value>2011-01-23T09:15:37.60Z</value>
    </time>
    <waveformID networkCode="IR" stationCode="LPAZ"></waveformID>
    <onset>emergent</onset>
    <phaseHint>Sn</phaseHint>
  </pick>
  <magnitude publicID="smi:ISC/magid=602398394">
    <mag>
      <value>3.80</value>
      <uncertainty>0.40</uncertainty>
    </mag>
    <type>Ml</type>
    <originID>smi:ISC/origid=601808754</originID>
    <stationCount>2</stationCount>
    <creationInfo>
      <author>SCB</author>
    </creationInfo>
  </magnitude>
  <preferredMagnitudeID>smi:ISC/magid=602398394</preferredMagnitudeID>

Will you have any idea to improve the code?

Tonino

what about, try for event in root.findall('origin'): for origin in event.findall('quality'): azimuthal_gap = origin.find('azimuthalGap').text — chickity china chinese chicken
– chickity china chinese chicken, Commented Dec 6, 2024 at 4:45

Hermann12 · Accepted Answer · 2024-12-06 06:22:10Z

2

If you have a list of events, you can create the interested gaps list with root.findall().

import xml.etree.ElementTree as ET

root = ET.parse("your_file.xml").getroot()

gaps = root.findall(".//azimuthalGap")
print([x.text for x in gaps])

Output:

['353.000', '453.000', …]

For the 3. point of your question, you will find a answer here.

edited Dec 6, 2024 at 6:22

answered Dec 6, 2024 at 6:00

Hermann12

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Comments

solari · Accepted Answer · 2024-12-06 06:35:41Z

1

With a simpler method:

with open("SCB_earthquakes.xml", "r") as infile:
    lines = infile.read().split("\n")
    for line in lines:
        if '<azimuthalGap>' in line:
            gaps.append(line.split('<azimuthalGap>')[1].split('<')[0])

answered Dec 6, 2024 at 6:35

solari

538 bronze badges

2 Comments

Parfait Dec 7, 2024 at 0:13

Consider parsing XML with DOM methods and not as a generic text file. Will save you headaches!

solari Dec 7, 2024 at 20:24

@Parfait Yes, DOM method is maybe better in case of a more complicated xml, but now it seems simple this way.

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