在没有参数的函数中调用函数

Question

快速提问：

我想在不带任何参数的情况下调用一个main函数，在main函数中，我还有其他几个函数有参数。我该怎么做呢？

以下是多个功能：

 # Takes the Portfolio dictionay, unpacks the multiple tuples, and calculates
 # the total price of the shares at time of purchase

def total_purchase_price(portfolio):
    totalprice = 0
    totalpurprice = 0
    for item in portfolio:
        purdate, purprice, numshares, sym, curprice = item
        totalprice += purprice * numshares
        totalpurprice = totalprice
    return totalpurprice

# Takes the Portfolio dictionay, unpacks the multiple tuples, and calculates
# the current total value of the shares

def total_value(portfolio):
    totalprice = 0
    totalvalueprice = 0
    for item in portfolio:
        purdate, purprice, numshares, sym, curprice = item
        totalprice += curprice * numshares
        totalvalueprice = totalprice
    return totalvalueprice   

# Takes the previous two functions, and subtracts them to get the total
# gain/lost of the shares

def total_gain(total_purchase_price, total_value, portfolio):
    gainlost = total_value - total_purchase_price
    return gainlost

例如，我现在所拥有的（注意：我知道这是行不通的，只是为了我想要的，因为每个函数都返回一个值）：

def testQ1(total_purchase_price, total_value, total_gain, portfolio):
    print("Total Cost =", total_purchase_price)
    print("Current Value =", total_value)
    print("Total gain/lost =", total_gain)
    return

例如，我想实现的目标：

def testQ2():
    total_purchase_price(portfolio)
    total_value(portfolio)
    total_gain(total_purchase_price, total_value, portfolio)
    print("Total Cost =", total_purchase_price)
    print("Current Value =", total_value)
    print("Total gain/lost =", total_gain)
    return   

我该怎么做？谢谢

Answer 1

portfolio是testQ2中唯一没有计算的参数。你需要有一个全局值，或者读入（可能在另一个函数中）。计算后，按适当的顺序返回值。

def testQ2():
    portfolio = getPortfolio()
    tp = total_purchase_price(portfolio)
    tv = total_value(portfolio)
    tg = total_gain(tp, tv, portfolio)
    print("Total Cost =", tp)
    print("Current Value =", tv)
    print("Total gain/lost =", tg)
    return portfolio, tp, tv, tg

Answer 2

使用类可能更容易：

class PortfolioParser:
    def __init__(self, portfolio):
        self.portfolio = portfolio
        self.price = self.total_purchase_price()
        self.value = self.total_value()
        self.gain = self.total_gain()

    def total_purchase_price(self):
        # Takes the Portfolio dictionay, unpacks the multiple tuples, and calculates
        # the total price of the shares at time of purchase
        totalprice = 0
        totalpurprice = 0
        for item in self.portfolio:
            purdate, purprice, numshares, sym, curprice = item
            totalprice += purprice * numshares
            totalpurprice = totalprice
        return totalpurprice      

    def total_value(self):
        # Takes the Portfolio dictionay, unpacks the multiple tuples, and calculates
        # the current total value of the shares
        totalprice = 0
        totalvalueprice = 0
        for item in self.portfolio:
            purdate, purprice, numshares, sym, curprice = item
            totalprice += curprice * numshares
            totalvalueprice = totalprice
        return totalvalueprice   

    def total_gain(self):
        # Takes the previous two functions, and subtracts them to get the total
        # gain/lost of the shares
        return self.value- self.price

    def testQ2(self):
        print("Total Cost = {0}\nCurrent Value = {1}\nTotal Gains = {2}".format(self.price, self.value, self.gain))

然后你可以这样使用它：

myPortfolio = # The portfolio to parse
parser = PortfolioParser(myPortfolio)
parser.testQ2()