[英]Function returning different result despite the same inputs in Python
這是我的 function,它使用 Poloniex Exchange API。 它獲取詢問(價格和金額的元組)的dict
,然后計算使用給定支出將獲得的 BTC 總量。
但是多次運行 function 會返回不同的金額,盡管要求和支出保持不變。 這個問題應該可以通過多次打印“詢問”(定義如下)和 function 結果來復制。
def findBuyAmount(spend):
#getOrderBook
URL = "https://poloniex.com/public?command=returnOrderBook¤cyPair=USDT_BTC&depth=20"
#request the bids and asks (returns nested dict)
r_ab = requests.get(url = URL)
# extracting data in json format -> returns a dict in this case!
ab_data = r_ab.json()
asks = ab_data.get('asks',[])
#convert strings into decimals
asks=[[float(elem[0]), elem[1]] for elem in asks]
amount=0
for elem in asks: #each elem is a tuple of price and amount
if spend > 0:
if elem[1]*elem[0] > spend: #check if the ask exceeds volume of our spend
amount = amount+((elem[1]/elem[0])*spend) #BTC that would be obtained using our spend at this price
spend = 0 #spend has been used entirely, leading to a loop break
if elem[1]*elem[0] < spend: #check if the spend exceeds the current ask
amount = amount + elem[1] #BTC that would be obtained using some of our spend at this price
spend = spend - elem[1]*elem[0] #remainder
else:
break
return amount
如果 asks 字典中的第一個問題是[51508.93591717, 0.62723766]
並且花費是1000
,我預計金額等於(0.62723766/51508.93591717) * 1000
但我會得到各種不同的輸出。 我怎樣才能解決這個問題?
您會得到各種不同的輸出,因為每次運行 function 時都會獲取新數據。 將獲取和計算拆分為單獨的函數,以便您可以獨立測試它們。 您還可以通過正確命名變量來使邏輯更清晰:
import requests
def get_asks(url="https://poloniex.com/public?command=returnOrderBook¤cyPair=USDT_BTC&depth=20"):
response = requests.get(url=url)
ab_data = response.json()
asks = ab_data.get('asks', [])
#convert strings into decimals
return [(float(price), qty) for price, qty in asks]
def find_buy_amount(spend, asks):
amount = 0
for price, qty in asks:
if spend > 0:
ask_value = price * qty
if ask_value >= spend:
amount += spend / price
spend = 0
else:
amount += qty
spend -= ask_value
else:
break
return amount
asks = get_asks()
print("Asks:", asks)
print("Buy: ", find_buy_amount(1000, asks))
當要價超過剩余支出時,您的數學是錯誤的; 此時訂單簿上的數量無關緊要,因此您可以購買的數量只是spend / price
。
隨着功能的拆分,您還可以對同一個訂單簿運行任意次數的find_buy_amount
,並看到結果實際上總是相同的。
問題在於您的“我們沒有足夠的錢”路徑。 在這種情況下,您可以購買的數量並不取決於提供的數量。
if elem[1]*elem[0] > spend:
amount += spend/elem[0]
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