How to indicate that data feed is live data

[Shiva]

Hello, I am new to python and also to Backtrader, I am able to develop python program to fetch live feeds from alphavantage and inserting the feed to MySQL database. I can fetch the data from MySQL also and use it in backtrader for backtesting. But I need cerebro to consider the same feed as live. My code below shows demo implementation.

class MySQLdata(DataBase):
    params = (
        ('dbHost', None),
        ('dbUser', None),
        ('dbPwd', None),
        ('dbPort', '3306'),
        ('dbName', None),
        ('ticker', "SBIN.NS"),
        ('historical', False),
        ('sessionend', None),
        ('fromdate', datetime.datetime.min),
        ('todate', datetime.datetime.max),
        ('name', ""),
        )

    def __init__(self):
        self.engine = create_engine('mysql+mysqlconnector://'+ self.p.dbUser + ':' + self.p.dbPwd + '@' + self.p.dbHost +
                                    ':' + self.p.dbPort + '/'+self.p.dbName
                                    + '?charset=utf8mb4', echo=False)

    def start(self):
        self.conn = self.engine.connect()
        self.result = self.conn.execute(
        
                   "SELECT `price_date`,`open_price`,`high_price`,`low_price`,`close_price`,`volume` FROM `daily_price_in` WHERE `symbol_id` = 'SBIN.NS' " + " AND `price_date` between '" + self.p.fromdate.strftime(
                "%Y-%m-%d") + "' and '" + self.p.todate.strftime("%Y-%m-%d") + "' ORDER BY `price_date` ASC")


    def stop(self):
        self.engine.dispose()

    def _load(self):
        one_row = self.result.fetchone()
        if one_row is None:
            return False

        self.lines.datetime[0] = date2num(one_row[0]) # for intraday data, time also need to be combined here.
        self.lines.open[0] = float(one_row[1])
        self.lines.high[0] = float(one_row[2])
        self.lines.low[0] = float(one_row[3])
        self.lines.close[0] = float(one_row[4])
        self.lines.volume[0] = int(one_row[5])
        self.lines.openinterest[0] = -1
        return True

    def islive(self):
        return True


if __name__ == "__main__":


    data = MySQLdata(dbHost = '127.0.0.1',
                     dbUser = 'root',
                     dbPwd = 'bala',
                     dbName = 'securities_master',
                     sessionstart=datetime.time(9, 0),
                     sessionend=datetime.time(16, 0)
                     )

    # --- use case for Alphavantage data feed ---

    cerebro = bt.Cerebro()
    cerebro.addstrategy(TestStrategy)
    cerebro.adddata(data)

    cerebro.broker.setcash(100000.00)

    # Add a FixedSize sizer according to the stake
    cerebro.addsizer(bt.sizers.FixedSize, stake=100)

    cerebro.run(live=True)
    # cerebro.run()

    # cerebro.plot(style='candle', numfigs=1, volup='green', voldown='red',
    #              voltrans=75.0, voloverlay=False)

def start(self):
    self.conn = self.engine.connect()
    self.result = self.conn.execute(
        "SELECT `price_date`,`open_price`,`high_price`,`low_price`,`close_price`,`volume` FROM `daily_price_in` WHERE `symbol_id` = 'SBIN.NS' " + " AND `price_date` between '" + self.p.fromdate.strftime(
            "%Y-%m-%d") + "' and '" + self.p.todate.strftime("%Y-%m-%d") + "' ORDER BY `price_date` ASC")


def stop(self):
    self.engine.dispose()

def _load(self):
    one_row = self.result.fetchone()
    if one_row is None:
        return False

    self.lines.datetime[0] = date2num(one_row[0]) # for intraday data, time also need to be combined here.
    self.lines.open[0] = float(one_row[1])
    self.lines.high[0] = float(one_row[2])
    self.lines.low[0] = float(one_row[3])
    self.lines.close[0] = float(one_row[4])
    self.lines.volume[0] = int(one_row[5])
    self.lines.openinterest[0] = -1
    return True

def islive(self):
    return True

if name == "main":

data = MySQLdata(dbHost = '127.0.0.1',
                 dbUser = 'xxxx',
                 dbPwd = '****',
                 dbName = 'securities_master',
                 sessionstart=datetime.time(9, 0),
                 sessionend=datetime.time(16, 0)
                 )



cerebro = bt.Cerebro()
cerebro.addstrategy(TestStrategy)
cerebro.adddata(data)

cerebro.run(live=True)
```

I need to modify _load method to return None so as to indicate cerebro that feed is live and wait till the MySql DB is filled with data and it is once again called in cerebro.

Thanks