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I'm trying to use XPath to extract a node from a XML file, by looking for a specific value in one of its subnodes.

I have a XML file from this location: Hourly forecasts for selected locations

Here is a part from it:

<HourlyLocationsForecast> <Identification> <Organization>Israel Meteorological Service</Organization> <Title>Hourly forecasts for selected locations</Title> <IssueDateTime>Tue Dec 10 06:30:40 IST 2019</IssueDateTime> </Identification> <Location> <LocationMetaData> <LocationName>AFULA NIR HAEMEQ</LocationName> <LocationLatitude>32.596</LocationLatitude> <LocationLongitude>35.277</LocationLongitude> <LocationHeight>60</LocationHeight> </LocationMetaData> <LocationData> <Forecast> <ForecastTime>10/12/2019 04:00 UTC</ForecastTime> <Temperature>11.3</Temperature> <RelativeHumidity>100</RelativeHumidity> <WindSpeed>1.4</WindSpeed> <WindDirection>34</WindDirection> </Forecast> <Forecast> <ForecastTime>10/12/2019 05:00 UTC</ForecastTime> <Temperature>11.7</Temperature> <RelativeHumidity>100</RelativeHumidity> <WindSpeed>1.5</WindSpeed> <WindDirection>31</WindDirection> </Forecast> <Forecast> <ForecastTime>10/12/2019 06:00 UTC</ForecastTime> <Temperature>13.8</Temperature> <RelativeHumidity>100</RelativeHumidity> <WindSpeed>1.3</WindSpeed> <WindDirection>27</WindDirection> </Forecast> </LocationData> </Location> <Location> <LocationMetaData> <LocationName>AVDAT</LocationName> <LocationLatitude>30.788</LocationLatitude> <LocationLongitude>34.771</LocationLongitude> <LocationHeight>555</LocationHeight> </LocationMetaData> <LocationData> <Forecast> <ForecastTime>10/12/2019 04:00 UTC</ForecastTime> <Temperature>10.5</Temperature> <RelativeHumidity>95</RelativeHumidity> <WindSpeed>1.2</WindSpeed> <WindDirection>238</WindDirection> </Forecast> <Forecast> <ForecastTime>10/12/2019 05:00 UTC</ForecastTime> <Temperature>11.6</Temperature> <RelativeHumidity>91</RelativeHumidity> <WindSpeed>1.4</WindSpeed> <WindDirection>251</WindDirection> </Forecast> <Forecast> <ForecastTime>10/12/2019 06:00 UTC</ForecastTime> <Temperature>13.9</Temperature> <RelativeHumidity>83</RelativeHumidity> <WindSpeed>1.5</WindSpeed> <WindDirection>258</WindDirection> </Forecast> </LocationData> </Location> <Location> <LocationMetaData> <LocationName>BEER SHEVA</LocationName> <LocationLatitude>31.251</LocationLatitude> <LocationLongitude>34.799</LocationLongitude> <LocationHeight>279</LocationHeight> </LocationMetaData> <LocationData> <Forecast> <ForecastTime>10/12/2019 04:00 UTC</ForecastTime> <Temperature>12.2</Temperature> <RelativeHumidity>98</RelativeHumidity> <WindSpeed>0.7</WindSpeed> <WindDirection>136</WindDirection> </Forecast> <Forecast> <ForecastTime>10/12/2019 05:00 UTC</ForecastTime> <Temperature>12.6</Temperature> <RelativeHumidity>95</RelativeHumidity> <WindSpeed>0.7</WindSpeed> <WindDirection>145</WindDirection> </Forecast> </LocationData> </Location> </HourlyLocationsForecast>

I want to extract full weather forecast just for a specific city. The city name is stored under /Location/LocationMetaData/LocationName, while the actuael data is under /Location/LocationData.

After looking at this question: XPath: Select first element with a specific attribute, I tried to use this XPath string:

//HourlyLocationsForecast/Location[@LocationMetaData/LocationName='JERUSALEM CENTRE']

I assumed I can relate to a value in a subnode as well as a value of an attribute in the node itself.

I get 'No Match' as an answer.

What am I doing wrong?

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1 Answer 1

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Two problems:

  1. LocationMetaData is an element, not an attribute, so remove the preceding @.
  2. JERUSALEM CENTRE appears nowhere in your XML at all, so filter instead on a LocationName that actually exists (e.g. AFULA NIR HAEMEQ).

This corrected XPath,

//HourlyLocationsForecast/Location[LocationMetaData/LocationName='AFULA NIR HAEMEQ']

would actually select something given your XML.

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1 Comment

Thanks for that! I removed the @ and got exactly what I wanted. Now it's //HourlyLocationsForecast/Location[LocationMetaData/LocationName='JERUSALEM CENTRE']. And about the 'JERUSALEM CENTRE' - you're right. it's in the full file (which I linked into) and not in the snippest I've pasted here.

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