isbuy in SIzer is always True. Why?

Roman Semko

Hi guys, I am struggling with a simple example. Maybe someone else had a similar issue. I am creating a simple sizer. My problem is that it always passes True for isbuy, even for sell. Here a dead-simple example to showcase the problem:

import os
import datetime
from core.yahoo import getf  # My own function, returns path to a file of ticker data.
import backtrader as bt
from random import randint

class Sizer(bt.Sizer):
    def _getsizing(self, comminfo, cash, data, isbuy):
        print '     ISBUY?', isbuy
        return 1
    
class Strategy(bt.Strategy):
    def next(self):
        if randint(0, 1):
            print 'BUY'
            self.buy()
        else:
            print 'SELL'
            self.sell()

# getf is a function that returns a path to the file, where yahoo data has been downloaded into.
datapath = os.path.join(os.getcwd(), getf('VGT'))  
data = bt.feeds.YahooFinanceCSVData(
    dataname=datapath,
    fromdate=datetime.datetime(2007, 1, 1),
    todate=datetime.datetime(2012, 12, 31),
    reverse=True)

cerebro = bt.Cerebro()
cerebro.addstrategy(Strategy)
cerebro.addsizer(Sizer)
cerebro.adddata(data)
cerebro.broker.setcash(5000.0)
cerebro.run()

The result? isbuy is always true!

BUY
     ISBUY? True
BUY
     ISBUY? True
SELL
     ISBUY? True
BUY
     ISBUY? True
SELL
     ISBUY? True
SELL
     ISBUY? True
SELL
     ISBUY? True
BUY
     ISBUY? True

Am I doing something wrong?

Thanks for any help!

backtrader

Nothing. This is a bug introduced recently when refactoring other parts to allow mixed used of buy / sell and the order_target_xxx family.

Fixed now with this commit: https://github.com/mementum/backtrader/commit/b119eaa073d09817e13809e2a439034debc75821

Roman Semko

Wow. That was quick! Thank you! ^^

backtrader

Together with the additions to filling in plotting and the new oanda orders, enough to make a quick release:

Community - Release 1.9.43.116