用tkinter写一个汇率转换

好的，下面是一个简单的汇率转换器的示例代码，使用 Python 的 tkinter 模块实现 GUI：

import tkinter as tk
import requests

class CurrencyConverter:
    def __init__(self, url):
        self.data = requests.get(url).json()
        self.currencies = self.data['rates']

    def convert(self, from_currency, to_currency, amount):
        initial_amount = amount
        if from_currency != 'USD':
            amount = amount / self.currencies[from_currency]
        # limiting the precision to 4 decimal places
        amount = round(amount * self.currencies[to_currency], 4)
        return amount

class App:
    def __init__(self, master):
        self.master = master
        self.converter = CurrencyConverter('https://api.exchangerate-api.com/v4/latest/USD')
        master.title("Currency Converter")

        # create dropdown boxes for currencies
        self.from_currency = tk.StringVar(master)
        self.to_currency = tk.StringVar(master)

        from_currency_dropdown = tk.OptionMenu(master, self.from_currency, *self.converter.currencies.keys())
        to_currency_dropdown = tk.OptionMenu(master, self.to_currency, *self.converter.currencies.keys())

        from_currency_dropdown.grid(row=0, column=0, padx=5, pady=5)
        to_currency_dropdown.grid(row=0, column=1, padx=5, pady=5)

        # create entry widget for amount
        self.amount = tk.Entry(master)
        self.amount.grid(row=1, column=0, padx=5, pady=5)

        # create button to perform conversion
        self.convert_button = tk.Button(master, text="Convert", command=self.perform_conversion)
        self.convert_button.grid(row=1, column=1, padx=5, pady=5)

        # create label to display converted amount
        self.converted_amount = tk.Label(master, text="")
        self.converted_amount.grid(row=2, column=0, columnspan=2, padx=5, pady=5)

    def perform_conversion(self):
        amount = float(self.amount.get())
        from_currency = self.from_currency.get()
        to_currency = self.to_currency.get()

        converted_amount = self.converter.convert(from_currency, to_currency, amount)

        self.converted_amount.config(text=str(converted_amount))

root = tk.Tk()
app = App(root)
root.mainloop()

这个程序使用 exchangerate-api.com 提供的 API 获取货币汇率数据，然后在 GUI 中提供下拉列表、输入框和按钮，让用户输入转换前的货币种类、转换后的货币种类以及转换金额，最后显示转换后的金额。