Solved the error this way....Correct way? def MACD_color(data): MACD_color = [] # for i in range ( 0 , len (data)): for i in range ( 0 , len (data)): if i== 0 : MACD_color. append (False) if i> 0 : if data[ 'MACDh_12_26_9' ][i] > data[ 'MACDh_12_26_9' ][i - 1 ]: MACD_color. append (True) else : MACD_color. append (False) return MACD_color