urllib2 error 'Not found on Accelerator'

Question

I have a python program that periodically checks the weather from weather.yahooapis.com, but it always throws the error: urllib.HTTPError: HTTP Error 404: Not Found on Accelerator. I have tried on two different computers with no luck, as well as changing my DNS settings. I continue to get the error. Here is my code:

#!/usr/bin/python

import time
#from Adafruit_CharLCDPlate import Adafruit_CharLCDPlate
from xml.dom import minidom
import urllib2

#towns, as woeids
towns = [2365345,2366030,2452373]

val = 1
while val == 1:
time.sleep(2)
for i in towns:
    mdata = urllib2.urlopen('http://206.190.43.214/forecastrss?w='+str(i)+'&u=f')
    sdata = minidom.parseString(mdata)
    atm = sdata.getElementsByTagName('yweather:atmosphere')[0]
    current = sdata.getElementsByTagName('yweather:condition')[0]
    humid = atm.attributes['humidity'].value
    tempf = current.attributes['temp'].value
    print(tempf)
    time.sleep(8)

I can successfully access the output of the API through a web browser on the same computers that give me the error.

Answer 1

The problem is that you're using the IP address 206.190.43.214 rather than the hostname weather.yahooapis.com.

Even though they resolve to the same host (206.190.43.214, obviously), the name that's actually in the URL ends up as the Host: header in the HTTP request. And you can tell that this makes the difference here:

$ curl 'http://206.190.43.214/forecastrss?w=2365345&u=f'
<404 error>
$ curl 'http://weather.yahooapis.com/forecastrss?w=2365345&u=f'
<correct rss>
$ curl 'http://206.190.43.214/forecastrss?w=2365345&u=f' -H 'Host: weather.yahooapis.com'
<correct rss>

If you test the two URLs in your browser, you will see the same thing.

---

So, in your code, you have two choices. You can use the DNS name instead of the IP address:

mdata = urllib2.urlopen('http://weather.yahooapis.com/forecastrss?w='+str(i)+'&u=f')

… or you can use the IP address and add the Host header manually:

req = urllib2.Request('http://206.190.43.214/forecastrss?w='+str(i)+'&u=f')
req.add_header('Host', 'weather.yahooapis.com')
mdata = urllib2.urlopen(req)

---

There's least one other problem in your code once you fix this. You can't call minidom.parseString(mdata) when mdata is a urlopen thingy; you either need to call read() on the thingy, or use parse instead of parseString.