如何制作一个程序，输入字典并输出银行净额？

Question

我正在尝试写一个程序，这个程序可以接收一个字典作为输入，然后输出银行账户的净金额。

我试过以下代码，但输出结果不对，我也搞不清楚为什么：

netAmount = 0
bankDict = {'D':300,'D':300,'W':200,'D':100}
operations = bankDict.keys()
amount = bankDict.values()
for i in range(len(operations)):
    if operations[i] == 'D': netAmount += amount[i]
    elif operations[i] == 'W': netAmount -= amount[i]
else: pass
print netAmount
# OUTPUT: -100

输入不一定非得是字典。

Answer 1

这个问题可以用另一种方法来解决：

def calculate_net_amount(trans_list):
    net_amount = 0 
    for i in trans_list:
        if(i[0] == 'D'):
            net_amount = net_amount + int(i[2::])
        elif(i[0] == 'W'):
            net_amount = net_amount - int(i[2::])
    return net_amount

trans_list=["D:300","D:200","W:200","D:100"]
print(calculate_net_amount(trans_list))

Answer 2

我刚想起来，我之前问过一个关于机器人位置的类似问题。现在，下面的代码可以正常工作：

netAmount = 0
operations = ['D','D','W','D']
amount = [300,300,200,100]
i = 0

while i < (len(operations)):
    if operations[i] == 'D': netAmount += amount[i]
    elif operations[i] == 'W': netAmount -= amount[i]
    else: pass
    i += 1

Answer 3

你仍然可以传入一个字典，只需要把它改成

bank_dict = {'D':[300, 300, 100],
             'W':[200]
            }

然后你可以通过计算每个键对应的值列表的总和来调整账户余额。

Answer 4

字典不会为同一个键存储两个不同的条目。所以当你用多个条目创建 bankDict，而这些条目的键都是 "D" 时，它只会保存最后一个条目：

In [149]: bankDict = {'D':300,'D':300,'W':200,'D':100}

In [150]: bankDict
Out[150]: {'D': 100, 'W': 200}

你可能希望把交易记录存成一个列表：

In [166]: transactions = [{"type": "deposit", amount: 300}, {"type": "deposit", amount: 300}, {"type": "withdrawal", amount: 200}, {"type": "deposit", amount: 100}]

In [167]:for transaction in transactions:
            if(transaction["type"] == "deposit"):
                netAmount += transaction["amount"]
            elif(transaction["type"] == "withdrawal"):
                netAmount -+ transaction["amount"]

你甚至可以把字典中的交易提取出来，放到一个单独的类里。