@rajanprabu Can I understand the mechanism as: the SMA indicator can be put in init section of the ibtest.py example because the build-in SMA indicator implemented the "next" method. When live data fits in, Cerebro calls the next() method of the SMA indicator to update the indicator value. Is it correct?

Thanks rajanprabu and vladisld. That means, if live data is involved, and I want my backtesting strategy to be reusable in live data environment, I can't put my indicator calculations (usually in the form of array operations) in init. I must rewrite those indicators as methods, which accepts data feeds in each iteration of "next"

I'm going to add live data fetching to my code. I read the example "sample\ibtest\ibtest.py" and have a question:

In the class: TestStrategy of the sample code, it contain a SMA calculation in the init of the TestStrategy class:

self.sma = bt.indicators.MovAv.SMA(self.data, period=self.p.smaperiod)

Because the init run once only (during the TestStrategy class instance creation). However, the real time data (i.e. self.data) updates continuously, how can the "self.sma" be reflected, as init run once only?

Thank you, rajanprabu. You're right, I'm using a wrong bracket...

I'm a newbie to Backtrader and just developed my first custom indicator (I mainly follow the samples at https://community.backtrader.com/topic/2145/full-example-of-custom-indicator/5)

However, when I try to compare indicator values, e.g. lazy is my custom indicator, and I try to compare the values of itself one units ago, i.e.

    self.lazy(-1)>self.lazy(0)

I got the following error message:

bool should return bool, returned LineOwnOperation

I know the custom indicator is actually a line object. How can I get the value of it?