def handle_data(context, data): 
           # Take a 100% long position in AAPL
           order_target_percent(context.aapl, 1.00) 

The order_target_percent function is a very blunt instrument and can often not do what you expect. If you have pending orders, it'll still order, then you'll wind up with more positions then you wanted, then you'll sell some next time.

Any time you want to order_target_percent, you really want to check to see if you already have some:
    

open_orders = get_open_orders()
    if context.aapl not in open_orders:
        order_target_percent(context.aapl, 1.0)

Same with selling. Make sure you don't already have a position trying to sell, or you'll quickly find yourself with some pending sells that account for all of your shares, then you go and short another 100% of your portfolio.