变量不随时间积累？

Question

好吧,我是python的新手,我正在学校上课,我对此有点困惑.我们正在编写一个程序/脚本来计算买卖股票的交易,由于某种原因,我无法获得"余额"变量随着时间的推移积累并从买卖股票中减去并增加.这是代码.任何输入都会很棒^.^

def main():

    #Below is the variables used in the context

    balance = float(input("Starting cash amount? "))
    numtrades = int(input("Number of trades for today?"))
    print('You do not own any shares, but have', balance, 'in cash')
    buy = 0
    sell = 0
    price_per_share = 0
    transaction_amount = 0
    transaction_amount_buy = 0
    transaction_amount_sell = 0


    #Below is the prompt for the first transaction, which requires a buy

    num_shares = int(input('Number of shares to buy?'))
    price_per_share = float(input('Price per share?'))
    print(num_shares, "shares for $",price_per_share, "per share cost $",price_per_share * num_shares)
    buy = buy + num_shares
    transaction_amount_buy = transaction_amount_buy + (num_shares * price_per_share)
    print("Currently holding", buy, "and have $", balance - transaction_amount_buy , "in cash")


    if balance < transaction_amount :

            print('You do not have sufficient funds to purchase', num_shares, 'for $', price_per_share, 'per share.')
            print('Your current balance is', balance, ', but', num_shares,' x ', price_per_share,' = ', num_shares * price_per_share)
            print("Currently holding", buy, "and have $", balance - transaction_amount , "in cash")




    #Below is the loop counter for each trade, along with if statements for buy/sell


    for i in range(numtrades):
        print('Trade number', (i + 2), end = "")
        action = input(' (buy/sell)?')
        if action == 'buy':
            num_shares = int(input('Number of shares to buy?'))
        if action == 'sell':
            num_shares = int(input('Number of shares to sell?'))
        price_per_share = float(input('Price per share?'))
        print('Transaction', (i+2))
        print('Transaction type is', action)


        if action == 'buy':
            print(num_shares, "shares for $",price_per_share, "per share cost $",price_per_share * num_shares)
            buy = buy + num_shares
            transaction_amount_buy = transaction_amount_buy + (num_shares * price_per_share)

        if action == 'sell':
            print(num_shares, 'shares for $',price_per_share, 'per share worth $',price_per_share * num_shares)
            sell = sell + num_shares
            transaction_amount_sell = transaction_amount_sell + (num_shares * price_per_share)

        transaction_amount = transaction_amount_buy - transaction_amount_sell

        if balance < transaction_amount :

            print('You do not have sufficient funds to purchase', num_shares, 'for $', price_per_share, 'per share.')
            print('Your current balance is', balance - transaction_amount, ', but', num_shares,' x ', price_per_share,' = ', num_shares * price_per_share)
            print("Currently holding", buy, "and have $", balance - transaction_amount , "in cash")


        if balance > transaction_amount :
            print("Currently holding", buy, "and have $", balance - transaction_amount , "in cash")

 main()

Answer 1

您打印差异,balance - transaction_amount但您从未将此值设置为balance变量.差不多,你做的事情与:

>>> cupcakes = 5
>>> print("I ate one cupcake, now I have", cupcakes - 1, "cupcakes")
I ate one cupcake, now I have 4 cupcakes
>>> print(cupcakes)
5 # We never modified the variable cupcakes

在打印语句之前,执行balance = balance - transaction_amount(或balance -= transaction_amount),然后在print函数中放入balance.