Using response.out.write from within an included file in Google App Engine

I think this is quite an easy question to answer, I just haven't been able to find anywhere detailing how to do it.

I'm developing a GAE app.

In my main file I have a few request handlers, for example:

class Query(webapp.RequestHandler):
    def post(self):
        queryDOI = cgi.escape(self.request.get('doiortitle'))
        import queryCosine
        self.response.out.write(queryCosine.cosine(queryDOI))

In that handler there I'm importing from a queryCosine.py script which is doing all of the work. If something in the queryCosine script fails, I'd like to be able to print a message or do a redirect.

Inside queryCosine.py there is just a n开发者_JAVA百科ormal Python function, so obviously doing things like

self.response.out.write("Done")

doesn't work. What should I use instead of self or what do I need to include within my included file? I've tried using Query.self.response.out.write instead but that doesn't work.

A much better, more modular approach, is to have your queryCosine.cosine function throw an exception if something goes wrong. Then, your handler method can output the appropriate response depending on the return value or exception. This avoids unduly coupling the code that calculates whatever it is you're calculating to the webapp that hosts it.

Pass it to the function.

main file:

import second

 ...
  second.somefunction(self.response.out.write)

second.py:

def somefunction(output):
  output('Done')