Small problem when trading with a lot of different length datas

mpskowron

I came into a problem while trading a lot of different length data. I am using MomentumOscilator, with a period as a parameter. I am trading big number of different datas, which have different lengths, so sometimes it happens that len(datas[i]) < period for some datas. Currently, I am just filtering the data in the init method, because MomentumOscilator code is throwing an exception while it is instantiating the data. When I checked the code, it actually seems like really simple change to fix this, in backtrader.linebuffer._once method:

        self.preonce(0, self._minperiod - 1)
        self.oncestart(self._minperiod - 1, self._minperiod)
        self.once(self._minperiod, self.buflen())

could be changed to:

        self.preonce(0, self._minperiod - 1)
        self.oncestart(self._minperiod - 1, min(self.buflen(), self._minperiod))
        self.once(self._minperiod, self.buflen())

Chapachan

@mpskowron May be that this helps: https://www.backtrader.com/docu/mixing-timeframes/indicators-mixing-timeframes.html

I'm not sure if it is applicable also to length datas, but it is designed for timeframes of different length