Question

I have a basic script that can parse the temperature, dew point, altimeter, etc. However, how can I parse a conditional string like the sky condition? I’d like to parse the data and have it print: “Sky Condition: few at 2000 ft AGL” for example.

import xml.etree.ElementTree as ET
from urllib import urlopen

link = urlopen('http://weather.aero/dataserver_current/httpparam?dataSource=metars&       requestType=retrieve&format=xml&stationString=KSFO&hoursBeforeNow=1')

tree = ET.parse(link)
root = tree.getroot()

data = root.findall('data/METAR')
for metar in data:
    print metar.find('temp_c').text

Answer 1

The page you are retrieving has a structure something like this:

<METAR>
  <!-- snip -->
  <sky_condition sky_cover="FEW" cloud_base_ft_agl="2000"/>
  <sky_condition sky_cover="BKN" cloud_base_ft_agl="18000"/>
</METAR>

So what you are asking is how to extract XML attributes. The xml.etree.ElementTree docs states that these are stored in a dictionary called attrib. So your code would look something like this:

data = root.findall('data/METAR')
for sky in data.findall('sky_condition'):
    print "Sky Condition: {0} at {1} ft AGL".format(
        sky.attrib['sky_cover'],
        sky.attrib['cloud_base_ft_agl']
      )