macd.py

signal = stock_data['macds'] # Your signal line
macd   = stock_data['macd']  # The MACD that need to cross the signal line
advice = ["No data"]    # Since you need at least two hours in the for loop

for i in range(1, len(signal)):
    # If the MACD crosses the signal line upward
    if macd[i] > signal[i] and macd[i - 1] <= signal[i - 1]:
        advice.append("BUY")
    # The other way around
    elif macd[i] < signal[i] and macd[i - 1] >= signal[i - 1]:
        advice.append("SELL")
    # Do nothing if not crossed
    else:
        advice.append("HOLD")

stock_data['advice'] = advice
print(stock_data['advice'])