Attribute Error: 'int' object has no attribute 'set'

Carson Lansdowne

Hello,

I am trying to modify the sizer within my strategy and I am using the code exactly as stated in the docs from backtrader, but I get the error:

File "anaconda3\lib\site-packages\backtrader\strategy.py", line 1449, in setsizer
    sizer.set(self, self.broker)

AttributeError: 'int' object has no attribute 'set'

I've tried to trouble shoot, but the documentation is not really much help as to what this error could be. How do I change my sizer based on a variable passed to the strategy class?

Here is my code

import backtrader as bt
import datetime
import math

class buynhold_1(bt.Strategy):
    params = (
        ('start_date', None),
        ('end_date', None),
        ('sizer', None),
        )
    
    def __init__(self):
        self.dataclose = self.datas[0].close()
        if self.p.sizer is not None:
            self.sizer = self.p.sizer

and here is how I am calling my code

cerebro.adddata(data)

# Set our desired cash start
cerebro.broker.setcash(1000.0)

# Add strategy to Cerebro
cerebro.addstrategy(buynhold_1,
                        start_date = datetime.datetime(2016,1,17),
                        end_date = datetime.datetime(2017,1,20),
                        sizer = 2
                        )

#add the sizer
#cerebro.addsizer(bt.sizers.SizerFix, stake=2)

if __name__ == '__main__':
    # Run Cerebro Engine
    start_portfolio_value = cerebro.broker.getvalue()

    cerebro.run()

Soham Jain

Hey Carson,
I guess you are confused between sizer and size.
sizer is a python class that comes with the backtrader module.
size is the quantity that you want to buy during a specific self.buy() call.

In order to derive the size to be bought logically, you must create a sub class that inherits from bt.Sizer base class.

import backtrader as bt

class FixedSize(bt.Sizer):
    params = (('stake', 1),)

    def _getsizing(self, comminfo, cash, data, isbuy):
        return self.params.stake

something like this...