Question

I am running the following code; it is from the Twisted Framework’s example list and is of a webserver.

from twisted.web import server, resource
from twisted.internet import reactor

class HelloResource(resource.Resource):
    isLeaf = True
    numberRequests = 0

    def render_GET(self, request):
        self.numberRequests += 1
        request.setHeader("content-type", "text/plain")
        arg = request.args
        q = arg['q']

        #Added for debugging
        for key, value in arg.iteritems():
            print key, value

        return "I am request #" + str(self.numberRequests) + " " + q[0] + "\n"

reactor.listenTCP(8080, server.Site(HelloResource()))
reactor.run()

To execute:

[user@localhost pytwist]$ python twi.py

Browser URL:

http://localhost:8080/?q=test

However, I am getting the following KeyError Exception on the console:

File "twi.py", line 12, in render_GET
q = arg['q']
exceptions.KeyError: 'q'

Yet, the browser is giving expected output:

I am request #3 test

Also, the console is properly displaying the debug part of the code:

q ['af']

If the output is correct and the key exists properly, then what could be the error? Note that I have tried dict.get() method but the problem persists.

Answer 1

It’s probably because your browser is making two requests. The second request is probably for the favicon.ico file, and here it doesn’t send the q parameter.

Try printing the URL requested.

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