Issue with RollOver and live data

BobDenar

Hi,

I had an issue with live data and RollOver data feed, and I think I found where is the problem.
Can you please review it and maybe submit a patch if relevant.

The live feed is my own class (Reuters). It returns None when no data is available yet and False when this is the end of the feed (I believe this is a convention here). I am trying to trade futures with my live feed and RollOver, but a problem arises on line 155 of feeds/rollover.py:

def _load(self):
    while self._d is not None:
        if not self._d.next():  # no values from current data source
            if self._ds:
                self._d = self._ds.pop(0)
                self._dts.pop(0)
            else:
                self._d = None
            continue

The test on if not self._d.next(): is ambigous as it makes no difference between None and False.
As a result if in a resampling, on say 5 seconds, no ticks came, then RollOver thinks the contract is over and get to the next one, which is wrong.

The solution I propose is to test False on this line:

def _load(self):
    while self._d is not None:
        if self._d.next() is False:  # no values from current data source
            if self._ds:
                self._d = self._ds.pop(0)
                self._dts.pop(0)
            else:
                self._d = None
            continue

It works great on both live data feed and backtest data feeds.
Thanks

backtrader

Indeed. I guess at that time ... such a feat was not even considered.

BobDenar

Hi,

I'm glad you've fixed this issue in the latest release.
Unfortunately, there is a typo in the check for values in the data source:

def _load(self):
    while self._d is not None:
        if self._d.next() is not False:  # no values from current data src
            if self._ds:
                self._d = self._ds.pop(0)
                self._dts.pop(0)
            else:
                self._d = None
            continue
            ...

It should have been:

def _load(self):
        while self._d is not None:
            if self._d.next() is False:  # no values from current data src
            ...

not was falsely added.

Regards

backtrader

Corrected. It will go into 1.9.67.122