How to deal with request that may timeout?

[Big Strong]

I have a  web.py application runs as  backgroud which provides some time-costing tasks. The task is triggered while receiving specific instructions from user. However, the response must be within 5s, or else the user would repeatedly post the request and result in repeated task executing. So it's there an asynchronous mechanism of web.py which can respond the user first then execute the task in background without being interrupted?