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What does this do?

what does the [-1[ in maavg below do and there can I find some reference for that? Thank in advance.

 maavg = talib.SMA(price_history, timeperiod=20)  
 if current_value > maavg[-1]  
1 response

Last element of the sequence maavg. You probably want to read a primer on python before diving into the Quantopian API too much further. Learning them simultaneously would be painful.