The purpose of this post is to see if there is an interest in forking backtrader into an ongoing and consolidated ‘living’ project.

Currently there are a number of reasons for this:

1. Backtrader’s creator has deservedly moved on to greener pastures and the original code is locked under his git account so no updates can be made. This will make the code stale over time and discourage new users.
2. There are minor bug fixes that need implementing and future ones will come up with changes in the world.
3. Many people have made great enhancements already implemented and they are not in the core system.
4. There are many forks in various stages of development fragmenting the project.
5. Backtrader needs to belong to the community now, not any one person.

I would propose that we create a central ‘new’ forked backtrader with a fresh start, start with a few keen people as administrators on git. I would suggest that the order of importance for implementing would be first bug fixes and second enhancements that already exist in the world.

We could invite people through this forum and active solicitation to bring the code enhancements to the new central backtrader.

After that, we can look at new improvements down the road. Who knows, maybe there are people out there who would be keen to work on such a project?

I would be prepared to house the new version and work on it. I’m hoping that in the beginning at least that some others might volunteer?

Backtrader is an awesome library and it will surely die if we don’t organize ourselves a bit.

Let me know your thoughts.

@damag00 From SO:
You need to handle your analyzer a bit differently. You can literally grab data at every bar and then have it available to you at the end.

Create a new analyzer, in my case I made:

class BarAnalysis(bt.analyzers.Analyzer):

In your analyzer in start you will create a new list.

def start(self):
    self.rets = list()

Then in next you will add a list of data for each bar. I use a try statement just in case there are any data problems, but it's probably not necessary. Strategy is included as as subclass and you can use its methods by calling self.strategy.getvalue() as an example.

def next(self):
    try:
        self.rets.append(
            [
                self.datas[0].datetime.datetime(),
                self.datas[0].open[0],
                self.datas[0].high[0],
                self.datas[0].low[0],
                self.datas[0].close[0],
                self.datas[0].volume[0],
                self.strategy.getposition().size,
                self.strategy.broker.getvalue(),
                self.strategy.broker.getcash(),
            ]
        )
    except:
        pass

Finally create a get_analysis method that you can use to get your results at the end.

def get_analysis(self):
    return self.rets

Add your analyzer to before running cerebro. You can name it whatever you want, we'll need the name to call the results.

cerebro.addanalyzer(BarAnalysis, _name="bar_data")

Make sure you provide a variable for the results of the cerebro.run() method so you can collect the results of the backtest.

strat = cerebro.run()

Finally, get the data out of strat and do as you wish with it. In this case I'm creating a dataframe and printing.

bar_data_res = strat[0].analyzers.bar_data.get_analysis()
df = pd.DataFrame(bar_data_res)
print(df)

And the printout looks like:

/home/runout/projects/rb_master/venv/bin/python /home/runout/projects/scratch/20210424_analyzer.py
                             0       1       2  ...  6         7         8
0   2020-01-02 23:59:59.999989  212.70  213.36  ...  0  10000.00  10000.00
1   2020-01-03 23:59:59.999989  210.81  213.28  ...  0  10000.00  10000.00
2   2020-01-06 23:59:59.999989  210.18  213.59  ...  0  10000.00  10000.00
3   2020-01-07 23:59:59.999989  213.11  214.13  ...  0  10000.00  10000.00
4   2020-01-08 23:59:59.999989  212.43  216.47  ...  0  10000.00  10000.00
..                         ...     ...     ...  ... ..       ...       ...
247 2020-12-23 23:59:59.999989  268.38  269.31  ...  1  10015.38   9747.25
248 2020-12-24 23:59:59.999989  267.76  269.67  ...  1  10016.48   9747.25
249 2020-12-28 23:59:59.999989  270.48  270.55  ...  1  10014.82   9747.25
250 2020-12-29 23:59:59.999989  268.30  268.78  ...  1  10011.78   9747.25
251 2020-12-30 23:59:59.999989  264.45  265.64  ...  1  10010.86   9747.25

[252 rows x 9 columns]

Process finished with exit code 0

The whole code looks like this:

import datetime
import backtrader as bt
import pandas as pd

class BarAnalysis(bt.analyzers.Analyzer):

    def start(self):
        self.rets = list()

    def next(self):
        try:
            self.rets.append(
                [
                    self.datas[0].datetime.datetime(),
                    self.datas[0].open[0],
                    self.datas[0].high[0],
                    self.datas[0].low[0],
                    self.datas[0].close[0],
                    self.datas[0].volume[0],
                    self.strategy.getposition().size,
                    self.strategy.broker.getvalue(),
                    self.strategy.broker.getcash(),
                ]
            )
        except:
            pass

    def get_analysis(self):
        return self.rets


class Strategy(bt.Strategy):

    params = (
        ("lowerband", 30),
        ("upperband", 70),
    )

    def __init__(self):
        self.rsi = bt.ind.RSI(period=10)

    def next(self):
        if not self.position:
            if self.rsi <= self.p.lowerband:
                self.buy()
        elif self.rsi >= self.p.upperband:
            self.close()

if __name__ == "__main__":

    cerebro = bt.Cerebro()

    ticker = "HD"
    data = bt.feeds.YahooFinanceData(
        dataname=ticker,
        timeframe=bt.TimeFrame.Days,
        fromdate=datetime.datetime(2020, 1, 1),
        todate=datetime.datetime(2020, 12, 31),
        reverse=False,
    )

    cerebro.adddata(data, name=ticker)

    cerebro.addanalyzer(BarAnalysis, _name="bar_data")
    cerebro.addstrategy(Strategy)

    # Execute
    strat = cerebro.run()

    bar_data_res = strat[0].analyzers.bar_data.get_analysis()
    df = pd.DataFrame(bar_data_res)
    print(df)

@appypollyloggies said in Cerebro forloop reuse?:

strategy = SmaCross(item[0],item[1])

I think your problem lies here. You are instantiating the strategy class. The strategy class is passed into cerebro as a class and with it the kwargs. Something like this.

for item in x:

        cerebro = bt.Cerebro()

        kwargs = dict(
             param1 = item[0],
             param2 = item[1], 
        )

        cerebro.addstrategy(SmaCross, **kwargs)

        data0 = bt.feeds.YahooFinanceData(dataname='MSFT', fromdate=datetime(2018, 1, 1),
                                          todate=datetime(2020, 12, 31))
        cerebro.adddata(data0)

        cerebro.run()

ta-lib is the python wrapper for the well established Technical Analysis Library external to backtrader.

Backtrader makes use of this library with it's own connection to the ta-lib. These indicators are also call TA-Lib in backtrader, hence more confusion. You will need ta-lib python wrapper installed to use this.

The last library is the very newly minted bta-lib. This was created by the maker of backtrader as a handy library for doing technical analysis when using pandas dataframes. In a nutshell, you can put in a OHLCV dataframe and BTA-LIB will spit out the indicator. It works quite well and is easier to use that the original ta-lib library.

@jas2210 Definitely use analyzers. You can collect a wide array of data into dictionaries/lists/tuples, etc.

Then at the end of your run, you can extract the analyzer, and then turn it into a dataframe.

Here's an example of an analyzer that collects closed trade information similar to what you are after:

class TradeClosed(bt.analyzers.Analyzer):
    """
    Analyzer returning closed trade information.
    """

    def start(self):
        super(TradeClosed, self).start()

    def create_analysis(self):
        self.rets = {}
        self.vals = tuple()

    def notify_trade(self, trade):
        """Receives trade notifications before each next cycle"""
        if trade.isclosed:
            self.vals = (
                self.strategy.datetime.datetime(),
                trade.data._name,
                round(trade.pnl, 2),
                round(trade.pnlcomm, 2),
                trade.commission,
                (trade.dtclose - trade.dtopen),
            )
            self.rets[trade.ref] = self.vals

    def get_analysis(self):
        return self.rets

You would implement when setting up cerebro using:

self.cerebro.addanalyzer(TradeClosed, _name="trade_closed")

You would then use the following line to get your data after the backtest runs:

trade_dict = results[0].analyzers.getbyname("trade_closed").get_analysis()

Finally, turn this into a dataframe:

columns_df = [
        "Date Closed",
        "Ticker",
        "PnL",
        "PnL Comm",
        "Commission",
        "Days Open",
    ]

df = pd.DataFrame(trade_dict)
df = df.T
df.columns = columns_df

When you get your dictionary to this stage, you need the datetime key and the second column, which is value, to send to quantstats.

You do this by creating a dataframe from the dictionary and then eliminating the cash column. Once you have this dataframe, you can then put it into your quantstats functions. I had success with a couple of the function but got an error on the reports.html tearsheet. This is a problem you'll have to debug in quantstats. ( I suspect this works more natively from inside Jupyter)

df_values = pd.DataFrame(results[0].analyzers.getbyname("cash_market").get_analysis()).T
    df_values = df_values.iloc[:, 1]
    qs.extend_pandas()

    qs.reports.html(df_values, "SPY", output="qs.png")
    # qs.plots.snapshot(df_values, "SPY")
    # print(qs.stats.sharpe(df_values))

Your question is unclear to me. Are you looking for trade position (number of units long or short), or if an order is buy sell?

For trade position in next use:

getposition(data=None, broker=None)

For order:
Strategy class offers three methods to assist you with orders.

User Methods:
    isbuy(): returns bool indicating if the order buys
    issell(): returns bool indicating if the order sells
    alive(): returns bool if order is in status Partial or Accepted

The code you've shared looks highly unorthadox for backtrader. Could we take a step back and you tell us what you are trying to accomplish in general, without any solutions? We can then tell you if maybe there's a better way to handle things.

I took the liberty of writing up the code.

import datetime
import backtrader as bt
import math

class LogReturns(bt.Indicator):
    params = (
        ("log_period", 1),
    )
    lines = ('logreturns',)

    def next(self):
        # This makes sure enough bars have passed before trying to calcualte the log return.
        if len(self) < self.p.log_period:
            return
        self.l.logreturns[0] = (math.log(self.datas[0].close[0] / self.datas[0].close[-1]) / self.p.log_period) * 100


class Strat(bt.Strategy):
    params = dict(log_period=1)

    def log(self, txt, dt=None):
        """ Logging function fot this strategy"""
        dt = dt or self.data.datetime[0]
        if isinstance(dt, float):
            dt = bt.num2date(dt)
        print("%s, %s" % (dt.date(), txt))

    # Added log return to the signal printout.
    def print_signal(self):
        self.log(
            "o {:7.2f}\th {:7.2f}\tl {:7.2f}\tc {:7.2f}\tlog_return {:3.3f}".format(
                self.datas[0].open[0],
                self.datas[0].high[0],
                self.datas[0].low[0],
                self.datas[0].close[0],
                self.lr[0],
            )
        )

    def __init__(self):
        self.lr = LogReturns(log_period=self.p.log_period)


    def next(self):
        self.print_signal()


if __name__ == "__main__":

    cerebro = bt.Cerebro()

    for s in ['AAPL']:
        data = bt.feeds.YahooFinanceData(
            dataname=s,
            timeframe=bt.TimeFrame.Days,
            fromdate=datetime.datetime(2019, 11, 4),
            todate=datetime.datetime(2020, 11, 4),
            reverse=False,
        )
        cerebro.adddata(data)

    cerebro.addstrategy(Strat)

    # Execute
    cerebro.run()

Which prints out something like:

2019-11-04, o   63.07	h   63.20	l   62.60	c   63.12	log_return -55.771
2019-11-05, o   63.01	h   63.29	l   62.83	c   63.03	log_return -0.143
2019-11-06, o   62.94	h   63.11	l   62.59	c   63.05	log_return 0.032
2019-11-07, o   63.61	h   64.01	l   63.46	c   63.78	log_return 1.151
2019-11-08, o   63.60	h   64.03	l   63.15	c   63.95	log_return 0.266
2019-11-11, o   63.50	h   64.53	l   63.50	c   64.46	log_return 0.794

When you create the order make your order equal to a variable, say: self.order Also keep track of the latest traillimit price with another variable, in this case self.trail_price.

You will need to initialize them as None. The changing limit can be found in the order as the created price, so order.created.price.

Just compare the created price to your tracking trail_price and you can print or log whenever they are not equal.

Here's full code implementation:

def next(self):

    if not self.position and self.buy_sig:
        self.order = self.buy(size=1, exectype=bt.Order.StopTrail, trailamount=5)
        self.trail_price = self.order.created.price
        self.log(
            f"ORDER MADE: close {self.data.close[0]}, trail price {self.trail_price}"
        )
    elif self.position and self.sell_sig:
        self.sell()
    else:
        pass

    if self.trail_price and self.order is not None:
        if self.trail_price != self.order.created.price:
            self.log(
                f"TRAIL PRICE CHANGES: \tclose {self.data.close[0]:.2f},"
                f"\told trail price {self.trail_price:.2f},"
                f"\tnew trail price {self.order.created.price:.2f}"
            )
            self.trail_price = self.order.created.price

Output:

2020-01-29 12:10:00, ORDER MADE: close 3274.75, trail price 3279.75
2020-01-29 12:25:00, TRAIL PRICE CHANGES: 	close 3274.50, 	old trail price 3279.75, 	new trail price 3279.50
2020-01-29 12:35:00, TRAIL PRICE CHANGES: 	close 3273.75, 	old trail price 3279.50, 	new trail price 3278.75
2020-01-29 13:00:00, TRAIL PRICE CHANGES: 	close 3273.25, 	old trail price 3278.75, 	new trail price 3278.25
2020-01-29 13:10:00, TRAIL PRICE CHANGES: 	close 3272.00, 	old trail price 3278.25, 	new trail price 3277.00
2020-01-29 13:30:00, BUY EXECUTED, Price: 3277.00, Cost: -3308.50, Comm 0.00

@jinwook-jang Have you looked here in the docs?

@littleking At line 315. https://github.com/neilsmurphy/backtrader_template/blob/main/main.py

@chewbacca Try this thread. https://community.backtrader.com/topic/2707/out-of-memory-error-when-running-optstrategy/8?_=1637411279547

@littleking Try this thread. https://community.backtrader.com/topic/2707/out-of-memory-error-when-running-optstrategy/8?_=1637411279547

@vladisld Sad situation.

@steven-veenma Right

@steven-veenma I have limited powers. Only able to change display name.

@adamb032 Trade position gets closed every time the units for the position reaches or crosses zero. See the docs here.

@duni4i It appears you are always adding the indicator to self.datas[0].

def __init__(self):
        self.zz = ZigZag(self.data0, period=2, retrace=0.05, minbars=2)

Try either

1. Change this to the second dataline

def __init__(self):
        self.zz = ZigZag(self.datas[1], period=2, retrace=0.05, minbars=2)

or
2. remove the lower time frame if you don't need it. This will move the resampled data to self.datas[0]

# cerebro.adddata(data0)   # remove

@steven-veenma I might be able to do this, what name do you want?