修改“货币兑换”程序，将货币兑换功能封装在CurExchange.py文件中，在01_test.py文件中使用CurExchange模块

要实现货币兑换功能的封装，我们可以创建一个名为 `CurExchange.py` 的Python文件，其中包含一个类，该类负责处理所有的货币兑换逻辑。然后在另一个文件 `01_test.py` 中导入 `CurExchange` 模块并使用它来进行货币兑换。

首先，我们来创建 `CurExchange.py` 文件：

# CurExchange.py

class CurrencyExchanger:
    def __init__(self, rates):
        # rates: a dictionary that holds exchange rates from a base currency to other currencies
        # e.g., rates = {'USD': 1, 'EUR': 0.86, 'JPY': 120}
        self.rates = rates

    def exchange(self, amount, from_currency, to_currency):
        # amount: the amount of money to be exchanged
        # from_currency: the currency code to exchange from
        # to_currency: the currency code to exchange to
        # Convert amount to the base currency first, then to the target currency
        base_rate = self.rates[from_currency]
        target_rate = self.rates[to_currency]
        if base_rate == 0 or target_rate == 0:
            raise ValueError("Invalid exchange rate.")
        base_amount = amount / base_rate
        exchanged_amount = base_amount * target_rate
        return exchanged_amount

现在，我们创建 `01_test.py` 文件来使用 `CurExchange` 模块：

# 01_test.py

from CurExchange import CurrencyExchanger

def main():
    # Define exchange rates
    rates = {'USD': 1, 'EUR': 0.86, 'JPY': 120}
    
    # Create a CurrencyExchanger instance
    exchanger = CurrencyExchanger(rates)
    
    # Exchange 100 USD to EUR
    result = exchanger.exchange(100, 'USD', 'EUR')
    print(f"100 USD is equal to {result:.2f} EUR")

    # Exchange 500 JPY to USD
    result = exchanger.exchange(500, 'JPY', 'USD')
    print(f"500 JPY is equal to {result:.2f} USD")

if __name__ == '__main__':
    main()

在这个例子中，我们定义了一个汇率字典，创建了一个 `CurrencyExchanger` 类的实例，并使用它来执行两次货币兑换操作。通过运行 `01_test.py`，我们可以看到兑换的结果。