如何从列表中获取值，然后在基本数学方程式中使用它？

Question

I am trying to take a float value from an api provided list. I was able to make it look like a float value when I print it but I don't think it is a true number because I cant use it in my math equation. There are other functions to get trailTrigger and stopLoss but I am happy that they work. I just can't get lastTradePrice to be a float I can use.

    # Call My last trade from Coinbase
def coinBaseMyLastTrade():
    global lastTradePrice
    global lastTradeSize
    global lastTradeFee
    global lastTradeSide
    global lastTradeSettled
    myLastTrade = requests.get(api_url + 'fills?product_id=BTC-USDC&limit=1', auth=auth)
    lastTradeList = myLastTrade.json()
    lastTradePrice = [float(lastTradeList_item['price']) for lastTradeList_item in lastTradeList]
    lastTradeSize = [float(lastTradeList_item['size']) for lastTradeList_item in lastTradeList]
    lastTradeFee = [float(lastTradeList_item['fee']) for lastTradeList_item in lastTradeList]
    lastTradeSide = [str(lastTradeList_item['side']) for lastTradeList_item in lastTradeList]
    lastTradeSettled = [lastTradeList_item['settled'] for lastTradeList_item in lastTradeList]
    print 'My Last Trade Price =',lastTradePrice
    print 'My Last Trade Size =',lastTradeSize
    print 'My Last Trade Fee =',lastTradeFee
    print 'My Last Trade Side =',lastTradeSide
    print 'My Last Trade Settled =',lastTradeSettled
    return

# Work out the value to use to trigger the trail loop
def calculateTrailTriggerValue():
    global triggerValue
    global stoplossValue
    if "buy" in lastTradeSide:
        triggerValue = lastTradePrice * ((100+trailTrigger)/100)
        stoplossValue = lastTradePrice * ((100-stoploss)/100)
    elif "sell" in lastTradeSide:
        triggerValue = lastTradePrice * ((100-trailTrigger)/100)
        stoplossValue = lastTradePrice * ((100+stoploss)/100)
    print 'Trail Trigger $=',triggerValue
    print 'Stop Loss $=',stoplossValue
    return

When I run the code I get the fault

triggerValue = lastTradePrice * ((100-trailTrigger)/100)
TypeError: can't multiply sequence by non-int of type 'float'

Its strange because I used this code on a different list and I was able to use the values but It doesn't work with the code i need help with

# Call 24hour stats
def coinBasePastDayStats():
    dayStats = requests.get('https://api.pro.coinbase.com/products/BTC-USDC/stats')
    dayHigh = float(dayStats.json()['high'])
    dayLow = float(dayStats.json()['low'])
    dayChange = dayHigh - dayLow
    global dayChangePercent
    dayChangePercent = (dayChange / dayHigh) * 100
    print 'Last 24hr High =', dayHigh
    print 'Last 24hr Low =', dayLow
    print 'Last 24hr Change =', dayChange
    print 'Last 24hr Change Percent =', {:.2f}".format(dayChangePercent),'%'
    return

If anyone could help me take a list value and use it in a basic math equation I would be very grateful. Cheers

Answer 1

If you want to multiply an entire list like this I'd suggest using numpy arrays

import numpy as np
arr = np.array([ i for i in range(10)])
arr *= 2

Answer 2

It looks like you are on the right track. But as the others have said you are doing the operation on the list itself and python doesn't support that.

Without the use of numpy you have to loop over the list and do the operation on each value in turn.