Twisted Documentation: Custom Response Codes

# Custom Response Codes

The previous example introduced `NoResource`, a Twisted Web error resource which responds with a 404 (not found) code. This example will cover the APIs that `NoResource` uses to do this so that you can generate your own custom response codes as desired.

First, the now-standard import preamble:

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    from twisted.web.server import Site
    from twisted.web.resource import Resource
    from twisted.internet import reactor

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 `Request` object has shown up in a couple of places, but so far we've ignored it. It is a parameter to the `getChild` API as well as to render methods such as `render_GET`. 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 `setResponseCode` method to - you guessed it - set the response's status code.

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    class PaymentRequired(Resource):
        def render_GET(self, request):
            request.setResponseCode(402)
            return "<html><body>Please swipe your credit card.</body></html>"

Just like the other resources I've demonstrated, this one returns a string from its `render_GET` method to define the body of the response. All that's different is the call to `setResponseCode` 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 `/buy`:

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    root = Resource()
    root.putChild("buy", PaymentRequired())
    factory = Site(root)
    reactor.listenTCP(8880, factory)
    reactor.run()

Here's the complete example:

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    from twisted.web.server import Site
    from twisted.web.resource import Resource
    from twisted.internet import reactor

    class PaymentRequired(Resource):
        def render_GET(self, request):
            request.setResponseCode(402)
            return "<html><body>Please swipe your credit card.</body></html>"

    root = Resource()
    root.putChild("buy", PaymentRequired())
    factory = Site(root)
    reactor.listenTCP(8880, factory)
    reactor.run()

Run the server and visit `http://localhost:8880/buy` in your browser. It'll look pretty boring, but if you use Firefox's View Page Info right-click menu item (or your browser's equivalent), you'll be able to see that the server indeed sent back a 402 response code.

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Version: 13.2.0