Multiple buys in a row?

[bioluminesceme]

I'm probably doing something stupid, but I'm testing basic things and I don't understand why I'm getting more than 1 buy in a row.. despite my if conditions.

I'm getting 2 or more buys in a row. Shouldn't it buy with all available cash, and then wait for the sell condition - because there is no money left to buy with? (and my if condition is not met in the first place)
If I print the broker cash amount it does show that it did not actually buy anything I think, but there seems to be something wrong with the math there too. the self._broker._cash gets printed after the buy or sell is executed, so shouldn't broker cash reflect that buy or sell? the first two prints show the initialamount..

It's a "buy when StochRSI is below 30, sell when StochRSI is over 70".

import pandas as pd
import talib
from backtesting import Backtest, Strategy

# download ticker data CSV from Yahoo, save in /data folder 
ticker = "ENTERTICKERSYMBOL" 

initialamount = 1000
tickerdata = pd.read_csv(f"data/{ticker}.csv", index_col="Date", parse_dates=True)

print(ticker)

class StochRSI(Strategy):
    stochrsisettings = [ 12, 9, 6, 3]

    def init(self):
        super().init()
        self.stoch = self.I(talib.STOCHRSI, self.data.Close, self.stochrsisettings[0], self.stochrsisettings[1], self.stochrsisettings[2], self.stochrsisettings[3])
    
    def next(self):
        super().next()
        current_date = self.data.index[-1]
        current_close = self.data.Close[-1]
    
        if not self.position and self.stoch < 30:
            print(f"{current_date} - Buy when StochRSI is below 30 at ${current_close}")
            self.buy()
            print(self._broker._cash)
        
        if self.position and self.stoch > 70:
            print(f"{current_date} - Sell when StochRSI is over 70 at ${current_close}")
            self.position.close()   
            print(self._broker._cash)   
    

bt = Backtest(tickerdata, StochRSI, cash=initialamount)
stats = bt.run()

print(stats)

bt.plot()

print output example (download last year of TSLA data from Yahoo)

2021-09-14 00:00:00 - Buy when StochRSI is below 30 at $744.48999
1000
2021-09-27 00:00:00 - Sell when StochRSI is over 70 at $791.359985
1000
2021-11-04 00:00:00 - Buy when StochRSI is below 30 at $1229.910034
1042.200012
2021-11-05 00:00:00 - Buy when StochRSI is below 30 at $1222.089966
1042.200012
2021-11-08 00:00:00 - Buy when StochRSI is below 30 at $1162.939941
1042.200012
2021-11-09 00:00:00 - Buy when StochRSI is below 30 at $1023.5
1042.200012
(?!?!)
2021-11-22 00:00:00 - Sell when StochRSI is over 70 at $1156.869995
1042.200012 (? it sold at 1156-1023 = 133 profit why is the broker cash amount still the same?)

[kernc]

Your assumptions are slightly misguided. When you place an order via buy() or close the position via Position.close(), the trading is actually done on next candle Open. This might not explain multiple buys in a row (i.e. why market-order orders aren't being filled), but have you tried Backtest(..., trade_on_close=True)?

[bioluminesceme]

Ah right, of course! It checks the Close so will trade the next day - that's the broker cash mystery solved.

(Except it still prints the same output if I change it to

bt = Backtest(tickerdata, StochRSI, cash=initialamount, trade_on_close=True)

But as long as it's internally doing the right math it's fine.

Does this also affect the 2+ buys in a row thing? Where it registers an "I should buy" on day 1 but something changes on day 2 that makes it so it gets 'skipped' ?