Is this expected `broker.getcash()` behavior?

[wayneadams]

Hey @happydasch ,

Thanks for putting together this v20 implementation in Backtrader!

I have a question about the expected behavior of Cerebro.broker.getcash(). I was trying to test calling into my Oanda account (practice) and just return the account balance.

In the first attempt, I did not add data to cerebro.

from __future__ import (absolute_import, division, print_function,unicode_literals)

import json
from datetime import datetime

import backtrader as bt
import btoandav20 as bto

if __name__ == '__main__':

    with open("config.json", "r") as file:
        config = json.load(file)

    storekwargs = dict(
        token=config["oanda"]["token"],
        account=config["oanda"]["account"],
        practice=config["oanda"]["practice"]
    )
    store = bto.stores.OandaV20Store(**storekwargs)

    cerebro = bt.Cerebro()
    cerebro.setbroker(store.getbroker())

    print(f'Starting Portfolio Value: {cerebro.broker.getcash()}')
    cerebro.run()
    print(f'Final Portfolio Value: {cerebro.broker.getcash()}')

As my account has $999.93, I EXPECTED the print statements to output:

Starting Portfolio Value: 999.93
Final Portfolio Value: 999.93

Instead, the ACTUAL output was:

Starting Portfolio Value: 0.0
Final Portfolio Value: 0.0

In my second attempt, I added data to cerebro.

from __future__ import (absolute_import, division, print_function,unicode_literals)

import json
from datetime import datetime

import backtrader as bt
import btoandav20 as bto

if __name__ == '__main__':

    with open("config.json", "r") as file:
        config = json.load(file)

    storekwargs = dict(
        token=config["oanda"]["token"],
        account=config["oanda"]["account"],
        practice=config["oanda"]["practice"]
    )
    store = bto.stores.OandaV20Store(**storekwargs)

    datakwargs = dict(
        historical=True,
        fromdate=datetime(2021, 9, 16),
        todate=datetime(2021, 9, 17),
        timeframe=bt.TimeFrame.Minutes,
        compression=1  
    )
    data = store.getdata(dataname="EUR_USD", **datakwargs)

    cerebro = bt.Cerebro()
    cerebro.adddata(data)
    cerebro.setbroker(store.getbroker())

    print(f'Starting Portfolio Value: {cerebro.broker.getcash()}')
    cerebro.run()
    print(f'Final Portfolio Value: {cerebro.broker.getcash()}')

And the ACTUAL output was:

Starting Portfolio Value: 0.0
Final Portfolio Value: 999.9265

Is this expected?

[wayneadams]

Or, do you think this the expected behavior or all stores/brokers in Backtrader? If so, then sorry for the trouble, I'll go bother those maintainers 😅

[happydasch]

it will get available as soon as the store gets started which happens when you run cerebro. If you need the cash available before, you can just fetch it manually from oanda:

something like:

acc_summary = store.oapi.account.summary(account_no)