Python/Tornado - call to classmethod

Question

Given this simple code where I declare a class and a functions inside it. In the main I try to call the function but the call is not made. I don't get any error but if I put a print in order to know if the call has happened nothing occurs.

models

class Balance(Document):
    gross_balance = FloatField(required=True, min_value=0, default=0)

    @classmethod
    def createBalance(cls, gross_balance):
        result = yield Balance.objects.create(gross_balance = gross_balance)
        result.save()
    @classmethod
    def sayHi(cls):
        print "Hi there"

main

from models import Balance

class CreateBalanceHandler(tornado.web.RequestHandler):

@tornado.gen.coroutine
def post(self):
    gross_balance = self.get_argument('gross_balance')
    Balance.createBalance(gross_balance)
    Balance.sayHi()
    self.redirect('/query/{}'.format(gross_balance))

What am I doing wrong? The sayHi function show its print but there's no reaction with createBalance.

Is that your actual indentation, with `createBalance` outside the class body? — user2357112, May 09 '16 at 16:17
Also, I'm not familiar with tornado, but that `Balance.createBalance(gross_balance)` call is only creating a coroutine, not executing any of its code. Are you supposed to `yield from` that coroutine or something? — user2357112, May 09 '16 at 16:18

kwarunek · Accepted Answer · 2016-05-10T01:10:42.830

Decorate createBalance with gen.coroutine to run it on ioloop. To wait until balance is created invoke it like yield Balance.createBalance() in RequestHandler

models

class Balance(Document):
    gross_balance = FloatField(required=True, min_value=0, default=0)

    # classmethod must be the most outter decorator (as well as staticmethod)

    @classmethod
    @tornado.gen.coroutine
    def createBalance(cls, gross_balance):
        result = yield Balance.objects.create(gross_balance = gross_balance)
        # AFAIR save returns future and also should be yielded
        # yield. result.save()
        result.save()

    @classmethod
    def sayHi(cls):
        print "Hi there"

main

from models import Balance

class CreateBalanceHandler(tornado.web.RequestHandler):

    @tornado.gen.coroutine
    def post(self):
        gross_balance = self.get_argument('gross_balance')
        yield Balance.createBalance(gross_balance)
        Balance.sayHi()
        self.redirect('/query/{}'.format(gross_balance))

Note: As I mentioned in snippet's comment, in motorengine the Document.save returns Future and probably you want to yield it as well, to wait until it has finished.

Python/Tornado - call to classmethod

models

main

1 Answers1