index out of range about qtpylib HOT 4 CLOSED

from qtpylib.algo import Algo
import pandas as pd
import sys
import threading
import datetime


class TestStrategy(Algo):
    def on_start(self):
        self.bar_count = dict.fromkeys(self.symbols, 0)
        self.start_time = datetime.datetime.now()
        self.counter = 0
        self.lock = threading.Lock()
        print("Started...")

    def on_bar(self, instrument):
        if not instrument:
            print('Recieved Null instrument.')
            return

        self.lock.acquire()
        bars = instrument.get_bars(28)
        print('-'*10, 'This is for instrument:', instrument.get_symbol(), '-'*10)
        elapsedTime =  datetime.datetime.now() - self.start_time
        print("Time passed since start:", divmod(elapsedTime.total_seconds(), 60))

        if len(bars.index):
            self.bar_count[instrument] = self.bar_count[instrument] + 1
            print(bars.tail(1))
        else:
            print('Recieved empty bars.')
        self.counter = self.counter + 1
        allbars = 0
        for symbl in self.symbols:
             allbars = self.bar_count[symbl] + allbars
        print(self.bar_count)
        print('Total number of on_bar called:', self.counter)    
        print('Total number of non empty bars recieved:', allbars)
        print('-'*50)
        self.lock.release()
        sys.stdout.flush()


if __name__ == "__main__":
    sp500 = pd.DataFrame.from_csv('../datas/sp500.csv', index_col = None)

    strategy = TestStrategy(
        bar_window = 28,
        #instruments = sp500.iloc[:,0].tolist()[0:98],
        instruments = ['MMM', 'T', 'ABBV', 'ABT', 'ACN', 'AGN', 'ALL', 'GOOG', 'GOOGL', 'MP', 'AMZN', 'AXP', 'AIG', 'AMGN', 'AAPL',
                        'BAC', 'BIIB', 'BLK', 'BA', 'BMY', 'CVS', 'COF'],
        resolution  = "1T" # 1Min bar resolution (Pandas "resample" resolutions)
    )
    strategy.run()

---------- This is for instrument: BAC ----------
Time passed since start: (50.0, 15.73700000000008)
                            open   high  close  volume    low symbol  \
datetime
2016-12-23 21:22:00+00:00  22.59  22.59  22.59       4  22.59    BAC

                          symbol_group asset_class  signal
datetime
2016-12-23 21:22:00+00:00          BAC         STK     NaN
{'AGN': 18, 'GOOGL': 15, 'ACN': 14, 'BLK': 18, 'ABBV': 19, 'COF': 11, 'MMM': 12,
 'AXP': 12, 'AIG': 13, 'AAPL': 28, 'GOOG': 14, 'AMZN': 19, 'T': 16, 'CVS': 16, '
ALL': 13, 'BMY': 13, 'BAC': 25, 'ABT': 19, 'AMGN': 17, 'BA': 16, 'MP': 0, 'BIIB'
: 14}
Total number of on_bar called: 343
Total number of non empty bars recieved: 342
--------------------------------------------------