In the quantopian, there's a small window to enter the initial cash.
I always feel this is annoying. Every time I need to set the initial cash = the notional amount in my algorithm.
Otherwise the whole backtest give me small return as a lot cash is not being used. why can't just discard the initial cash window?
And another problem is the margin problem. is there any margin check process before u go short or go long?
I don't see anything like that. It seems I can short as many as i want.?
I think the answer to your first question is no but I am not entirely confident in that answer. I can provide an answer to your second question. There is no margin check built-in. Add this function to your code and perform the check.
def marginRequirements(portfolio):
req = 0
for stock in portfolio.positions:
amount = portfolio.positions[stock].amount
last_price = portfolio.positions[stock].last_sale_price
if amount > 0:
req += .25 * amount * last_price
elif amount < 0:
if last_price < 5:
req += max(2.5 * amount, abs(amount * last_price))
else:
req += max(5 * amount, abs(0.3 * amount * last_price))
return req 
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