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<title>Twisted Documentation: Custom Response Codes</title>

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<h1 class="title">Custom Response Codes</h1>

The previous example introduced <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.error.NoResource.html" title="twisted.web.error.NoResource">NoResource</a></code>, a Twisted Web error

resource which responds with a 404 (not found) code. This example will

cover the APIs that <code>NoResource</code> uses to do this so that

you can generate your own custom response codes as desired.

First, the now-standard import preamble:

<pre class="python">1

from twisted.web.server import Site

from twisted.web.resource import Resource

from twisted.internet import reactor

</pre>

Now we'll define a new resource class that always returns a 402

(payment required) response. This is really not very different from

the resources that was defined in previous examples. The fact that it

has a response code other than 200 doesn't change anything else about

its role. This will require using the request object, though, which

none of the previous examples have done.

The <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.server.Request.html" title="twisted.web.server.Request">Request</a></code>

object has shown up in a couple of places, but so far we've ignored

it. It is a parameter to the <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.resource.Resource.getChild.html" title="twisted.web.resource.Resource.getChild">getChild</a></code> API as well as to

render methods such as <code>render_GET</code>. As you might have

suspected, it represents the request for which a response is to be

generated. Additionally, it also represents the response being

generated. In this example we're going to use its <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.http.Request.setResponseCode.html" title="twisted.web.http.Request.setResponseCode">setResponseCode</a></code> method to - you

guessed it - set the response's status code.

<pre class="python">1

class PaymentRequired(Resource):

def render_GET(self, request):

request.setResponseCode(402)

return "Please swipe your credit card."

</pre>

Just like the other resources I've demonstrated, this one returns a

string from its <code>render_GET</code> method to define the body of

the response. All that's different is the call to

<code>setResponseCode</code> to override the default response code,

200, with a different one.

Finally, the code to set up the site and reactor. We'll put an

instance of the above defined resource at <code>/buy</code>:

<pre class="python">1

root = Resource()

root.putChild("buy", PaymentRequired())

factory = Site(root)

reactor.listenTCP(8880, factory)

reactor.run()

</pre>

Here's the complete example:

<pre class="python"> 1

class PaymentRequired(Resource):

def render_GET(self, request):

request.setResponseCode(402)

return "Please swipe your credit card."

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root = Resource()

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root.putChild("buy", PaymentRequired())

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factory = Site(root)

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reactor.listenTCP(8880, factory)

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reactor.run()

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</pre>

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Run the server and visit <code>http://localhost:8880/buy</code> in

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your browser. It'll look pretty boring, but if you use Firefox's View

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Page Info right-click menu item (or your browser's equivalent), you'll

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be able to see that the server indeed sent back a 402 response

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code.

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