question about order_target() function, why it's not ordering the specified shares of the stock?

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As a newbie in quantopian, I wrote a simple test in handle_data() function,
def handle_data(context,data):
print("********the timestamp is",get_datetime(),"*******")
print("the cash before ordering is",context.portfolio.cash)
order_target(sid(270),100)
for item in context.portfolio.positions:
print("item is ", item,)
for position in context.portfolio.positions.itervalues():
print("position amount is",position.amount)
return

As a position.amount result for the stock sid(270), it's varying at each time instead of being a constant 100, can anyone help me to understand why is that? Thanks!

As a reference, below is the output:
2011-01-04 09:31 PRINT ('********the timestamp is', Timestamp('2011-01-04 14:31:00+0000', tz='UTC'), '****')
2011-01-04 09:31 PRINT ('the cash before ordering is', 100000.0)
2011-01-04 09:32 PRINT ('*****the timestamp is', Timestamp('2011-01-04 14:32:00+0000', tz='UTC'), '****')
2011-01-04 09:32 PRINT ('the cash before ordering is', 100000.0)
2011-01-04 09:33 PRINT ('*****the timestamp is', Timestamp('2011-01-04 14:33:00+0000', tz='UTC'), '*****')
2011-01-04 09:33 PRINT ('the cash before ordering is', 99988.4375376)
2011-01-04 09:33 PRINT ('item is ', Equity(270 [AKRX]))
2011-01-04 09:33 PRINT ('position amount is', **2)
2011-01-04 09:34 PRINT ('********the timestamp is', Timestamp('2011-01-04 14:34:00+0000', tz='UTC'), '*****')
2011-01-04 09:34 PRINT ('the cash before ordering is', 99675.70408650559)
2011-01-04 09:34 PRINT ('item is ', Equity(270 [AKRX]))
2011-01-04 09:34 PRINT ('position amount is', **56)
2011-01-04 09:35 PRINT ('********the timestamp is', Timestamp('2011-01-04 14:35:00+0000', tz='UTC'), '*****')
2011-01-04 09:35 PRINT ('the cash before ordering is', 99664.12162330559)
2011-01-04 09:35 PRINT ('item is ', Equity(270 [AKRX]))
2011-01-04 09:35 PRINT ('position amount is', **58)
.............

2 responses

victor tse

Hi Karl,

Thank you for the explanation. In order to understand how this order method works, I wrote a small piece of code (context.flag is initialized to be 0),

        print("---the timestamp is",get_datetime(),"---")  
        if context.flag==0:    # keep ordering if my share in hand is not reaching 5000  
            order_target(sid(24),10000)  
            print("bought!")  
        else:       #stop ordering if reaching 5000 shares  
            print("stop")

        print("position amount is",context.portfolio.positions[sid(24)].amount)  
        if context.portfolio.positions[sid(24)].amount>5000:  
            context.flag=1  
        elif context.portfolio.positions[sid(24)].amount<0:  
            context.flag=0  
    return

I would image the the portfolio position amount would stop right after reaching 5000, however, I end up getting 27340 shares of the stock as below.
May I know why is this happening? :)

2011-01-04 09:31 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:31:00+0000', tz='UTC'), '---')
2011-01-04 09:31 PRINT bought!
2011-01-04 09:31 PRINT ('position amount is', 0)
2011-01-04 09:32 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:32:00+0000', tz='UTC'), '---')
2011-01-04 09:32 PRINT bought!
2011-01-04 09:32 PRINT ('position amount is', 2110)
2011-01-04 09:33 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:33:00+0000', tz='UTC'), '---')
2011-01-04 09:33 PRINT bought!
2011-01-04 09:33 PRINT ('position amount is', 4307)
2011-01-04 09:34 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:34:00+0000', tz='UTC'), '---')
2011-01-04 09:34 PRINT bought!
2011-01-04 09:34 PRINT ('position amount is', 6243)
2011-01-04 09:35 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:35:00+0000', tz='UTC'), '---')
2011-01-04 09:35 PRINT stop
2011-01-04 09:35 PRINT ('position amount is', 7620)
2011-01-04 09:36 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:36:00+0000', tz='UTC'), '---')
2011-01-04 09:36 PRINT stop
2011-01-04 09:36 PRINT ('position amount is', 9670)
... 2011-01-04 09:48 PRINT ('position amount is', 27340)
2011-01-04 09:49 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:49:00+0000', tz='UTC'), '---')
2011-01-04 09:49 PRINT stop
2011-01-04 09:49 PRINT ('position amount is', 27340)
2011-01-04 09:50 PRINT ('---the timestamp is', Timestamp('2011-01-04 14:50:00+0000', tz='UTC'), '---')
2011-01-04 09:50 PRINT stop
2011-01-04 09:50 PRINT ('position amount is', 27340)

Dan Dunn

order_target doesn't evaluate open orders. So every time you print "bought!" you just placed an additional order. The traditional way to handle this is to check for open orders, and exit your ordering logic if you have open orders.

The better way to handle this is to use the Optimize API. The attached backtest uses the api, and it slims the ordering logic down to 3 lines. It's worth noting that the stock you're looking at there is a takeover target and will have some weird price and volume behavior - ordinarily we'd exclude stocks like that from our evaluations.

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