python - Return from @tornado.gen.engine function without yield? -

i'd execute or not execute async query based on value of parameter. if parameter true, query shouldn't executed.

i have method this:

@tornado.gen.engine def retrievesomedata(self, feelinglucky, callback):     if feelinglucky:         return      # <-- doesn't work, function never returns!     else:         response = yield tornado.gen.task(queryfunction, param1....)         callback(response) 

how can make feelinglucky branch work?

the thing can think of raising exception , catching in caller. that's ugly. or, if there such thing null task...

(python 2.7, tornado 3.2)

better use modern gen.coroutine instead of obsolete gen.engine. makes sort of conditional logic simple , natural:

@tornado.gen.coroutine def retrievesomedata(self, feelinglucky):     if feelinglucky:         return     else:         response = yield tornado.gen.task(queryfunction, param1....)         raise gen.return(response) 

if convert queryfunction coroutine style too, get:

@tornado.gen.coroutine def retrievesomedata(self, feelinglucky):     if feelinglucky:         return     else:         response = yield queryfunction(param1....)         raise gen.return(response)