How do I return HTTP error code without default template in Tornado?

It's better to use the standard interface and define your custom message on the HTTPError.

raise tornado.web.HTTPError(status_code=code, log_message=custom_msg)

You can then parse the error in your RequestHandler and check for the message:

class CustomHandler(tornado.web.RequestHandler):
    def write_error(self, status_code, **kwargs):
        err_cls, err, traceback = kwargs['exc_info']
        if err.log_message and err.log_message.startswith(custom_msg):
            self.write("<html><body><h1>Here be dragons</h1></body></html>")

You may simulate RequestHandler.send_error method:

class MyHandler(tornado.web.RequestHandler):
    def get(self):
        self.clear()
        self.set_status(400)
        self.finish("<html><body>My custom body</body></html>")

Tornado calls RequestHandler.write_error to output errors, so an alternative to VisioN's approach would be override it as suggested by the Tornado docs. The advantage to this approach is that it will allow you to raise HTTPError as before.

The source for RequestHandler.write_error is here. Below you can see an example of a simple modification of write_error that will change the set the status code and change the output if you provide a reason in kwargs. 

def write_error(self, status_code, **kwargs):
    if self.settings.get("serve_traceback") and "exc_info" in kwargs:
        # in debug mode, try to send a traceback
        self.set_header('Content-Type', 'text/plain')
        for line in traceback.format_exception(*kwargs["exc_info"]):
            self.write(line)
        self.finish()
    else:
        self.set_status(status_code)
        if kwargs['reason']:
            self.finish(kwargs['reason'])
        else: 
            self.finish("<html><title>%(code)d: %(message)s</title>"
                "<body>%(code)d: %(message)s</body></html>" % {
                    "code": status_code,
                    "message": self._reason,
                })

Tags:

Python

Tornado

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