Your choice. Be accurate with the first approach, it has look-ahead bias in it. So if your results will be very optimistic, than check them carefully.

@backtrader said in Best Approach for Live-Trading With Cheat on Open:

So it seems that I have to supply the --replay parameter in oandav20test.py.

I don't know. What you need is a data source which is tick based. You said you wanted to be notified of each price change. There should be no need to replay anything for that data feed.

Hi,

with samples/ibtest/ibtest.py I did some tests with Interactive Brokers livetrading. These are the results:

ibtest.py --data0 EUR.USD-CASH-IDEALPRO --timeframe Seconds --compression 30 --port 7497 --no-rightedge

***** DATA NOTIF: LIVE LIVE, Data0, 0962, 736801.8864360515, 2018-04-17T17:16:28.074845, 1.23699, 1.23699, 1.23699, 1.23699, 0, 0, 1.23703 LIVE, Data0, 0963, 736801.8866241798, 2018-04-17T17:16:44.329133, 1.237, 1.237, 1.237, 1.237, 0, 0, 1.237046 LIVE, Data0, 0964, 736801.8866485074, 2018-04-17T17:16:46.431042, 1.2371, 1.2371, 1.2371, 1.2371, 0, 0, 1.237034 LIVE, Data0, 0965, 736801.8866486517, 2018-04-17T17:16:46.443504, 1.237, 1.237, 1.237, 1.237, 0, 0, 1.237002 LIVE, Data0, 0966, 736801.886811497, 2018-04-17T17:17:00.513344, 1.23694, 1.23694, 1.23694, 1.23694, 0, 0, 1.237006 LIVE, Data0, 0967, 736801.8868541777, 2018-04-17T17:17:04.200952, 1.23693, 1.23693, 1.23693, 1.23693, 0, 0, 1.236994 LIVE, Data0, 0968, 736801.8869536915, 2018-04-17T17:17:12.798944, 1.23694, 1.23694, 1.23694, 1.23694, 0, 0, 1.236982 LIVE, Data0, 0969, 736801.8871321745, 2018-04-17T17:17:28.219872, 1.23691, 1.23691, 1.23691, 1.23691, 0, 0, 1.236944 LIVE, Data0, 0970, 736801.8871946137, 2018-04-17T17:17:33.614623, 1.23699, 1.23699, 1.23699, 1.23699, 0, 0, 1.236942 LIVE, Data0, 0971, 736801.8871946996, 2018-04-17T17:17:33.622046, 1.23698, 1.23698, 1.23698, 1.23698, 0, 0, 1.23695 LIVE, Data0, 0972, 736801.8871947962, 2018-04-17T17:17:33.630394, 1.23699, 1.23699, 1.23699, 1.23699, 0, 0, 1.236962 LIVE, Data0, 0973, 736801.8872731669, 2018-04-17T17:17:40.401621, 1.23698, 1.23698, 1.23698, 1.23698, 0, 0, 1.23697 LIVE, Data0, 0974, 736801.8872752264, 2018-04-17T17:17:40.579562, 1.23699, 1.23699, 1.23699, 1.23699, 0, 0, 1.236986 LIVE, Data0, 0975, 736801.8874047493, 2018-04-17T17:17:51.770338, 1.237, 1.237, 1.237, 1.237, 0, 0, 1.236988

ibtest.py --data0 EUR.USD-CASH-IDEALPRO --timeframe Seconds --compression 30 --port 7497 --resample

***** DATA NOTIF: LIVE LIVE, Data0, 0962, 736801.8892361111, 2018-04-17T17:20:30.000000, 1.23689, 1.23706, 1.23689, 1.23701, 0.0, 0, 1.2369620000000001 LIVE, Data0, 0963, 736801.8895833333, 2018-04-17T17:21:00.000000, 1.23702, 1.23703, 1.237, 1.23702, 0.0, 0, 1.23696 LIVE, Data0, 0964, 736801.8899305556, 2018-04-17T17:21:30.000000, 1.23701, 1.23707, 1.23699, 1.23707, 0.0, 0, 1.236974 LIVE, Data0, 0965, 736801.8902777778, 2018-04-17T17:22:00.000000, 1.23708, 1.23708, 1.23696, 1.23702, 0.0, 0, 1.237004

ibtest.py --data0 EUR.USD-CASH-IDEALPRO --timeframe Seconds --compression 30 --port 7497 --replay

***** DATA NOTIF: LIVE LIVE, Data0, 0962, 736801.8905911663, 2018-04-17T17:22:27.076771, 1.23694, 1.23694, 1.23694, 1.23694, 0.0, 0, 1.2369999999999999 LIVE, Data0, 0962, 736801.890625, 2018-04-17T17:22:30.000000, 1.23694, 1.23694, 1.23694, 1.23694, 0.0, 0, 1.2369999999999999 LIVE, Data0, 0963, 736801.8908331305, 2018-04-17T17:22:47.982471, 1.23693, 1.23693, 1.23693, 1.23693, 0.0, 0, 1.236982 LIVE, Data0, 0963, 736801.8908331448, 2018-04-17T17:22:47.983708, 1.23693, 1.23696, 1.23693, 1.23696, 0.0, 0, 1.236988 LIVE, Data0, 0963, 736801.8908638399, 2018-04-17T17:22:50.635766, 1.23693, 1.23698, 1.23693, 1.23698, 0.0, 0, 1.236992 LIVE, Data0, 0963, 736801.8908640771, 2018-04-17T17:22:50.656264, 1.23693, 1.23699, 1.23693, 1.23699, 0.0, 0, 1.236994 LIVE, Data0, 0963, 736801.8908658416, 2018-04-17T17:22:50.808718, 1.23693, 1.237, 1.23693, 1.237, 0.0, 0, 1.236996 LIVE, Data0, 0963, 736801.8908685311, 2018-04-17T17:22:51.041084, 1.23693, 1.23701, 1.23693, 1.23701, 0.0, 0, 1.236998 LIVE, Data0, 0963, 736801.8908700076, 2018-04-17T17:22:51.168654, 1.23693, 1.23702, 1.23693, 1.23702, 0.0, 0, 1.2369999999999999 LIVE, Data0, 0963, 736801.8908825091, 2018-04-17T17:22:52.248782, 1.23693, 1.23702, 1.23693, 1.23701, 0.0, 0, 1.236998 LIVE, Data0, 0963, 736801.890961202, 2018-04-17T17:22:59.047850, 1.23693, 1.23702, 1.23693, 1.23702, 0.0, 0, 1.2369999999999999 LIVE, Data0, 0963, 736801.8909623256, 2018-04-17T17:22:59.144933, 1.23693, 1.23704, 1.23693, 1.23704, 0.0, 0, 1.237004 LIVE, Data0, 0963, 736801.8909629615, 2018-04-17T17:22:59.199871, 1.23693, 1.23705, 1.23693, 1.23705, 0.0, 0, 1.2370059999999998 LIVE, Data0, 0963, 736801.890965801, 2018-04-17T17:22:59.445203, 1.23693, 1.23705, 1.23693, 1.23704, 0.0, 0, 1.237004 LIVE, Data0, 0963, 736801.8909722222, 2018-04-17T17:23:00.000000, 1.23693, 1.23705, 1.23693, 1.23704, 0.0, 0, 1.237004 LIVE, Data0, 0964, 736801.8909756911, 2018-04-17T17:23:00.299714, 1.23705, 1.23705, 1.23705, 1.23705, 0, 0, 1.2369999999999999 LIVE, Data0, 0964, 736801.8909989573, 2018-04-17T17:23:02.309913, 1.23705, 1.23705, 1.23704, 1.23704, 0.0, 0, 1.236998 LIVE, Data0, 0964, 736801.8910004616, 2018-04-17T17:23:02.439886, 1.23705, 1.23705, 1.23703, 1.23703, 0.0, 0, 1.236996

It seems to me, that the --replay parameter really delivers what I need:

tick based during live streaming after each candlestick timeframe, len(self.data0) increases by one and also the last call to next() for that block seems to comprise consistent values for OHLC for the whole candlestick.