Here is an example that uses two periods for buying/selling decisions. I didn't use booleans to determine the period behavior because they are quite brittle. If a state fails one time, the algorithm will break. Instead I used mod logic in this example to distinguish between timeperiods. Also, I gave it a window to buy and sell the stock. For example, if the algo cannot buy the stock exactly at 3PM (if there are not enough trades available) it will wait until 3:50PM to fill the purchase. This is more lenient and will give more flexibility in your algo. Of course, you can make the windows longer/shorter depending on your preferences.
For your second timeperiod, when you said "sell at 9:30 the next day" I interpreted this as selling the stock short since you already closed the position at 4PM in timeperiod 1. If this is incorrect, let me know and we'll create another version.
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