close position with some note

[kernc]

Discussed in #1298

^{Originally posted by silverwolf-x August 4, 2025}
I want to add reasons for the end of certain trades, for example, how do I tag the ending order of the buy trade from 2013-02-26, indicating that I ended the trade due to reason R, and write R into this order and trade.

from datetime import date
from backtesting import Backtest, Strategy
from backtesting.lib import crossover

from backtesting.test import SMA, GOOG
class SmaCross(Strategy):
    n1 = 10
    n2 = 20

    def init(self):
        close = self.data.Close
        self.sma1 = self.I(SMA, close, self.n1)
        self.sma2 = self.I(SMA, close, self.n2)

    def next(self):
        if not self.data.index[-1].date() >= date(2013, 2, 1):
            if crossover(self.sma1, self.sma2):
                self.position.close()
                self.buy()
            elif crossover(self.sma2, self.sma1):
                self.position.close()
                self.sell()
        else:
            if self.data.index[-1].date() == date(2013, 2, 26):
                self.buy(size=1, tag="2013-02-26buy")
            if self.data.index[-1].date() == date(2013, 2, 27):
                self.position.close()
bt = Backtest(GOOG, SmaCross, cash=10000, commission=0.002)

stats = bt.run()

My Hope:

when calling either self.position.close(reason="R") or self.trade.close(reason="R"), I want to update the tag of any canceled order to "R". This makes sense because, at that point, the order looks like this:

{
 'is_contingent': False,
 'is_long': False,
 'is_short': True,
 'limit': None,
 'parent_trade': <Trade size=34 time=2146- price=801.1- pl=173 tag=2013-02-26buy>,
 'size': -34.0,
 'sl': None,
 'stop': None,
 'tag': '2013-02-26buy',
 'tp': None
}

Since the order already contains a parent_trade, updating the tag to "R" clearly indicates that the reason for closing the trade was "R".

Additionally, it would be useful if trades included a new property: close_reason (e.g.), which would display "R" in such cases.