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