Python Calculate sum of x object attributes in a list

Question

I have a problem. I am trying to calculate the Moving Average over my list of candlesticks. To do so, I had something like this:

def calculate(ma, candlesticks):
    
    maData = []
    
    i = 0
    while i < len(candlesticks) - ma + 1:

        # Calculate the average of current window
        movingAverage = round(np.sum(candlesticks[i:i+ma]) / ma, 2)
        
        # Store the moving average
        maData.append(movingAverage)
        
        # Shift window to right by one position
        i += 1
  
    return maData

The problem I have is that the list of candlesticks contains objects with attributes. I need to calculate the moving average over the closes, so I thought I use:

movingAverage = round(np.sum(candlesticks[i:i+ma].close) / ma, 2)

But python says:

AttributeError: 'list' object has no attribute 'close'

The first round of this loop gives the following result when I print candlesticks[i:i+ma]:

[{'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1577836800000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 41.29, 'high': 42.08, 'low': 41.16, 'close': 41.16, 'volume': 110044.87445}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1577923200000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 41.58, 'high': 41.74, 'low': 39.17, 'close': 39.17, 'volume': 194486.2157}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578009600000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 39.44, 'high': 42.39, 'low': 38.77, 'close': 38.77, 'volume': 426771.00676}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578096000000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 42.23, 'high': 42.9, 'low': 41.77, 'close': 41.77, 'volume': 248814.62818}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578182400000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 42.79, 'high': 44.61, 'low': 42.6, 'close': 42.6, 'volume': 291964.84958}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578268800000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 43.29, 'high': 46.08, 'low': 43.16, 'close': 43.16, 'volume': 384930.9909}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578355200000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 45.8, 'high': 47.03, 'low': 44.48, 'close': 44.48, 'volume': 493847.10532}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578441600000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 46.3, 'high': 48.54, 'low': 44, 'close': 44, 'volume': 628050.68438}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578528000000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 45.35, 'high': 45.79, 'low': 43.9, 'close': 43.9, 'volume': 296221.65692}, {'dateTimeChanged': '2022-04-01T21:40:59.000Z', 'openTime': 1578614400000, 'symbol': 'LTCUSDT', 'interval': '1d', 'open': 44.75, 'high': 49.72, 'low': 43.71, 'close': 43.71, 'volume': 729803.12291}]

How can I use the attribute close of the candlestick list to calculate the moving avearge?

Answer 1

You cannot just access .close on the list, you need to access it on the individual elements. Instead of

candlesticks[i:i+ma].close

do

[candle.close for candle in candlesticks[i:i+ma]]

Answer 2

The problem is that candlesticks[i:i+ma] is an array of ma elements, that is why you can't access the close property. Instead, what you could do is

s = sum(candlesticks[i + j].close for j in range(ma))
movingAverage = round(s / ma, 2)

The nice thing about this is that you pass an iterator to the sum function, so you don't create an extra list to perform the addition.