python - 递归调用方法变量python

Question

我正在尝试生成一个从方法变量获取输入以递归方式填充的列表。（我相信）

我的代码：

class Register:
    cur_unit = [100, 50, 20, 10, 5, 1, .25, .10, .05, .01]
    reg_amount = []

    def load_reg(self):
        self.reg_amount = float(input('Enter amount of money in register...\n'))

    def transaction(self):
        trans_amount = float(input('Enter the cost of the transaction...\n'))
        if trans_amount > self.reg_amount:
            print("I'm sorry, but we don't have enough money in the register to allow this transaction...\n")
        else:
            cash_paid = float(input('Enter how much money you will pay with...\n'))
            change_due = cash_paid - trans_amount
            new_reg_amount = self.reg_amount - change_due
            if new_reg_amount < 0:
                print("I'm sorry, but we don't have enough money in the register to allow this transaction...\n")
            else:
                new_reg_amount = round(new_reg_amount, 2)
                change_due = round(change_due, 2)
                print('\n' + str(new_reg_amount))
                print(change_due)
                for i in self.cur_unit:
                    if change_due - i >= 0:
                        return [i] + [cash_paid - i]


reg = Register()
reg.load_reg()
res = reg.transaction()
print(res)

产生不良结果的结果：

Enter amount of money in register...
200
Enter the cost of the transaction...
24.24
Enter how much money you will pay with...
50

174.24
25.76
[20, 30.0] # undesired result

Process finished with exit code 0

如果可以从 cash_paid 中减去单位，而 change_due 不等于或小于 0，则期望的结果将贯穿 cur_unit 并带回每个单位：（这是需要的更多详细信息）

[20, 5, .25, .25, .25, .01]

标签： pythonrecursion

Answer 1

正如 Prune 在评论中指出的那样，这个问题通过迭代比递归更好地解决。万一你好奇，我写了两种方法：split_change_r它是一个递归函数，split_change是一个更清晰的迭代解决方案。请注意，他们假设您的cur_unit列表已经排序。

class Register:
    cur_unit = [100, 50, 20, 10, 5, 1, .25, .10, .05, .01]
    reg_amount = []

    def load_reg(self):
        self.reg_amount = float(input('Enter amount of money in register...\n'))

    def split_change_r(self, amount, l = []):
        next_cur = [a for a in self.cur_unit if a <= amount][0]
        if next_cur == amount:
            return l + [next_cur]
        else:
            # here is the recursive call
            return self.split_change_r(round(amount - next_cur, 2), l + [next_cur])

    def split_change(self, amount):
        r = []
        while(amount != 0):
            next_cur = [a for a in self.cur_unit if a <= amount][0]
            amount = round(amount - next_cur, 2)
            r.append(next_cur)
        return r


    def transaction(self):
        trans_amount = float(input('Enter the cost of the transaction...\n'))
        if trans_amount > self.reg_amount:
            print("I'm sorry, but we don't have enough money in the register to allow this transaction...\n")
        else:
            cash_paid = float(input('Enter how much money you will pay with...\n'))
            change_due = cash_paid - trans_amount
            new_reg_amount = self.reg_amount - change_due
            if new_reg_amount < 0:
                print("I'm sorry, but we don't have enough money in the register to allow this transaction...\n")
            else:
                new_reg_amount = round(new_reg_amount, 2)
                change_due = round(change_due, 2)
                print('\n' + str(new_reg_amount))
                print(change_due)
                return self.split_change(change_due)

reg = Register()
reg.load_reg()
res = reg.transaction()
print(res)

示例输出：

Enter amount of money in register...
200
Enter the cost of the transaction...
24.24
Enter how much money you will pay with...
50

174.24
25.76
[20, 5, 0.25, 0.25, 0.25, 0.01]