Check if ticker tradeable before all datafeeds are available

[mike_q]

Hi, community,

I have a Buy&Hold strategy which keeps the same portfolio weight during the whole strategy life. However, I want to start a strategy before all data feeds available. For example:
Allocation SPY - 50% and TLT -50%

• SPY is available on 01-01-1990
• TLT is available after 2004
  So in this situation, before 2004, I want to adjust allocation to SPY - 100% and once TLT is available, then use target allocation: SPY - 50% and TLT -50%

Below is a strategy I refer to. Do you know how to check if ticker is available for a given date. I think the best option is to implement such check during prenext call

import strategies
import logging
import backtrader as bt
from datetime import datetime
import sys

logging.basicConfig(level=logging.INFO,
                    format='%(asctime)s - %(name)s/%(funcName)s - %(levelname)s - %(message)s',
                    datefmt='%Y-%b-%d %H:%M:%S',
                    stream=sys.stdout)
logger = logging.getLogger(__name__)


class BuyHold(bt.Strategy):
    params = dict(allocation=None, rebalance_frequency=None)

    def __init__(self):
        self.allocation = self.params._get('allocation')
        logger.info(f'Set portfolio allocation to {self.allocation}')
        print('Date during init', self.data.datetime.datetime().date())
        for d in self.datas:
            print(f"stock: {d._name}, length: {len(d.array)}")

    def prenext(self):
        self.tradable_allocation()
        self.next()

    def tradable_allocation(self):
        tradable_alloc = dict()
        # for ticker in self.allocation:
        # if ticker is NOT tradable, then allocate asset weight to other ticker

        self.allocation = tradable_alloc

    def start(self):
        self.val_start = self.broker.get_cash()
        logger.info(f'Starting Portfolio Value: {self.broker.getvalue():.2f}')

    def next(self):
        for ticker in self.allocation:
            logger.debug(f'Execute Rebalance for {ticker} to {self.allocation[ticker]} allocation.')
            self.order_target_percent(ticker, target=self.allocation[ticker])
        self.allocation = self.params._get('allocation')  # Reset allocation on each step

    def stop(self):
        logger.info(f'Final Portfolio Value: {self.broker.getvalue():.2f}')


START_CASH = 10000.0
START_DATE = datetime(year=1990, month=12, day=2)
END_DATE = datetime(year=2005, month=12, day=31)
weights = dict(SPY=0.5, TLT=0.5)

if __name__ == '__main__':
    cerebro = bt.Cerebro()
    for ticker in weights:
        data = bt.feeds.YahooFinanceData(dataname=ticker,
                                         fromdate=START_DATE,
                                         todate=END_DATE)
        cerebro.adddata(data)

    cerebro.broker.setcash(START_CASH)

    # Run over everything
    cerebro.addstrategy(BuyHold, allocation=weights)
    results = cerebro.run()

[mike_q]

I found a way to check if data is available for a given date.

data = self.getdatabyname(ticker)
current_date = self.data.datetime.datetime().date()
if date == bt.num2date(data.datetime[0]).date():
  print(f'data is available for {ticker}')