Tornado中的`send_error`, `write_error`和`raise HTTPError`有什么区别?

Question

RT，官方文档看的不是很懂：
RequestHandler.send_error(status_code=500,kwargs)**
SendsthegivenHTTPerrorcodetothebrowser.
Ifflush()hasalreadybeencalled,itisnotpossibletosendanerror,sothismethodwillsimplyterminatetheresponse.Ifoutputhasbeenwrittenbutnotyetflushed,itwillbediscardedandreplacedwiththeerrorpage.
Overridewrite_error()tocustomizetheerrorpagethatisreturned.Additionalkeywordargumentsarepassedthroughtowrite_error.
RequestHandler.write_error(status_code,kwargs)**
Overridetoimplementcustomerrorpages.
write_errormaycallwrite,render,set_header,etctoproduceoutputasusual.
Ifthiserrorwascausedbyanuncaughtexception(includingHTTPError),anexc_infotriplewillbeavailableaskwargs["exc_info"].Notethatthisexceptionmaynotbethe“current”exceptionforpurposesofmethodslikesys.exc_info()ortraceback.format_exc.
我理解的是send_error调用了write_error，所以写自定义错误页面的时候要自己实现write_error方法，抛出错误的时候使用send_error。那么又该在什么时候使用rasietornado.web.HTTPError呢？

Answer 1

HTTPError一般是用tornado访问某个url，然后这个url不存在，或者返回一个错误码的时候用到的。fromtornado.httpclientimportHTTPClient,HTTPErrorhttp_client=HTTPClient()try:response=http_client.fetch(url,method='GET',request_timeout=120)exceptHTTPErrorashttp_error:printhttp_errorexceptExceptionase:printefinally:http_client.close()

Answer 2

send_error是Torando发送错误状态码到浏览器,而write_error是对自定义的错误页面进行重写,是2个不同的操作。