for ticker, df in dataframe.groupby('ticker'):
    self._all_data[ticker] = df.itertuples()

def _get_next_bar(self, ticker: str, datetime: pd.datetime):
    for bar in self._all_data[ticker]:
        if getattr(bar, 'time') == datetime:
            yield bar

def update_bars(self):
    date = next(self._get_next_datetime())
    for ticker in self.ticker_list:
        try:
            next_bar = next(self._get_next_bar(ticker, date))
        except StopIteration:
            self.continue_backtest = False
        else:
            if next_bar is not None:
                self.historic_data[ticker].append(next_bar)
                self.events.put(MarketEvent(ticker))

def _get_next_datetime(self):
    for datetime in self.all_datetimes:
        yield datetime