Python：从URL到CSV的XML检索

Question

I am trying to write a Python script that dynamically reads the XML data from a URL, (eg http://www.wrh.noaa.gov/mesowest/getobextXml.php?sid=KCQT&num=72 )

The format of the XML is as follows:

<station id="KCQT" name="Los Angeles / USC Campus Downtown" elev="179" lat="34.02355" lon="-118.29122" provider="NWS/FAA">
<ob time="04 Oct 7:10 pm" utime="1507169400">
<variable var="T" description="Temp" unit="F" value="61"/>
<variable var="TD" description="Dewp" unit="F" value="39"/>
<variable var="RH" description="Relh" unit="%" value="45"/>
</ob>
<ob time="04 Oct 7:05 pm" utime="1507169100">
<variable var="T" description="Temp" unit="F" value="61"/>
<variable var="TD" description="Dewp" unit="F" value="39"/>
<variable var="RH" description="Relh" unit="%" value="45"/>
</ob>
<ob time="04 Oct 7:00 pm" utime="1507168800">
<variable var="T" description="Temp" unit="F" value="61"/>
<variable var="TD" description="Dewp" unit="F" value="39"/>
<variable var="RH" description="Relh" unit="%" value="45"/>
</ob>
<ob time="04 Oct 6:55 pm" utime="1507168500">
<variable var="T" description="Temp" unit="F" value="61"/>
<variable var="TD" description="Dewp" unit="F" value="39"/>
<variable var="RH" description="Relh" unit="%" value="45"/>
</ob>
</station>

I only want to retrieve the timestamp and the decimal temperature ("Temp") for all the dates available (there are more than the 4 I included).

The output should be in a CSV formatted text file where the timestamps and temperature values are printed one pair per line.

Below is my attempt at the code (which is terrible and did not work at all):

import requests

weatherXML = requests.get("http://www.wrh.noaa.gov/mesowest/getobextXml.php?sid=KCQT&num=72")

import xml.etree.ElementTree as ET
import csv

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

# open file for writing
Time_Temp = open('timestamp_temp.csv', 'w')

#csv writer object
csvwriter = csv.writer(Time_Temp)
time_temp = []

count = 0
for member in root.findall('ob'):
    if count == 0:
        temperature = member.find('T').var
        time_temp.append(temperature)
        csvwriter.writerow(time_temp)
        count = count + 1

    temperature = member.find('T').text
    time_temp.append(temperature)

Time_Temp.close()

Please help.

Answer 1

You can iterate the element ob first, get the attribute time of element ob , and find element variable whose var is T and get the element value for temperature, append them to a list, and write it to csv files:

import xml.etree.ElementTree as ET
import csv
tree = ET.parse('getobextXml.php.xml')
root = tree.getroot()
# open file for writing
with open('timestamp_temp.csv', 'wb') as csvfile:
    csvwriter = csv.writer(csvfile)
    csvwriter.writerow(["Time","Temp"])
    for ob in root.iter('ob'): 
        time_temp = []
        timestamp = ob.get('time') #get the attribute time of element ob
        temp = ob.find("./variable[@var='T']").get('value') #find element variable which var is T, and get the element value
        time_temp.append(timestamp)
        time_temp.append(temp)
        csvwriter.writerow(time_temp) 

after that you can find timestamp_temp.csv will give you the result:

Time,Temp
04 Oct 8:47 pm,68
04 Oct 7:47 pm,68
04 Oct 6:47 pm,70
04 Oct 5:47 pm,74
04 Oct 4:47 pm,75
04 Oct 3:47 pm,75
04 Oct 2:47 pm,77
04 Oct 1:47 pm,78
04 Oct 12:47 pm,78
04 Oct 11:47 am,76
04 Oct 10:47 am,74
04 Oct 9:47 am,72
...

Answer 2

Assuming Python 3, this will work. I noted the Python 2 difference if needed:

import xml.etree.ElementTree as ET
import requests
import csv

weatherXML = requests.get("http://www.wrh.noaa.gov/mesowest/getobextXml.php?sid=KCQT&num=72")
root = ET.fromstring(weatherXML.text)

# Use this with Python 2
# with open('timestamp_temp.csv','wb') as Time_Temp:

with open('timestamp_temp.csv','w',newline='') as Time_Temp:
    csvwriter = csv.writer(Time_Temp)
    csvwriter.writerow(['Time','Temp'])
    for member in root.iterfind('ob'):
        date = member.attrib['time']
        temp = member.find("variable[@var='T']").attrib['value']
        csvwriter.writerow([date,temp])

Output:

Time,Temp
04 Oct 11:47 pm,65
04 Oct 10:47 pm,66
04 Oct 9:47 pm,68
04 Oct 8:47 pm,68
04 Oct 7:47 pm,68
04 Oct 6:47 pm,70
04 Oct 5:47 pm,74
04 Oct 4:47 pm,75
   .
   .