如何将没有括号和逗号的一行文本转储到 Pickle 文件中

Question

我正在编写一个货币转换器，其中一个部分是一个程序，它允许您检查和更改英镑与其他三种货币之间的转换率。虽然实际转换很好，但我在将新费率导出到单行的泡菜文件时遇到了问题。这是因为，费率以以下格式写入泡菜文件： 英镑 1 欧元 1.15 美元 1.3 等

我将不胜感激。

我试过简单地转储一个列表和元组，但它根本不起作用 - 这不是 Python 错误，而是一个逻辑错误。

import pickle

Currencies = "Pound-Sterling", "Euro", "US-Dollar", "Japanese-Yen"
Displayed = {}
Exchange_rates = pickle.load(open("rates.pkl","rb"))

print("This program allows you to check and change the currency conversion rates before using the converter program.")

for Line in Exchange_rates:
    if not "Pound-Sterling" in Line:
        Displayed_key = Line.split(" ")[0]
        Displayed_value = Line.split(" ")[1]
        Displayed[Displayed_key] = Displayed_value
        print("£1 is", Line)

Exchange_rates = {}
New_rates = open("rates.pkl","wb")
pickle.dump("",New_rates)
pickle.dump("Pound-Sterling 1",New_rates)

if getYesNo("Do you want to change an exchange rate for a currency (Y/N):"):
    for i in range(1,4):
        Currency = Currencies[i]
        print("£1 is", Currency, Displayed[Currency])
        Prompt = "Please input the new rate for", Currency, ":"
        Prompt = " ".join(Prompt)
        New_rate = float(input(Prompt))
        To_append = Currency, New_rate
        pickle.dump(To_append,New_rates)

New_rates.close()

新的 pickle 文件应该是单行的原始格式。相反，它要么在多行，要么不起作用，而且我无法摆脱括号和逗号。

Answer 1

这是您的代码版本，经过一些改进

改进：

1. 我们不想担心关闭文件，所以我们使用with open('Currencies.pkl', 'rb') as f:。这称为上下文管理器，负责关闭文件。
2. 我们想要重用的代码已被放入可调用函数中，例如print_currencies
3. 将for i in range(1,4): 更改为for currency in CURRENCIES: 更具可读性并且允许使用任意数量的货币。 CURRENCIES 这是一个字典，但可以是一个列表或任何可迭代的。
4. 我已经腌制了一个 Python 字典对象来存储货币。

需要改进的地方：

1. 我在代码中重复了“Currencies.pkl”
2. 我不问用户是否要关闭程序
3. 如果我想保持货币不变怎么办？

import pickle

# I'll use this later to test if pickle file exists
import os.path

# let's use a default dictionary object
CURRENCIES = {
    "Pound-Sterling": 1,
    "Euro": 1,
    "US-Dollar": 1,
    "Japanese-Yen": 1
}

def load_currencies():
    """Load a dictionary object of currencies previously stored"""
    with open('Currencies.pkl', 'rb') as f:
        dict = pickle.load(f)
    return dict

def dump_currencies(dict):
    """Dump a dictionary object of currencies"""
    with open('Currencies.pkl', 'wb') as f:
        pickle.dump(dict, f)

def print_currencies(dict):
    for currency in dict:
        if currency != "Pound-Sterling":
             print("£1 is", dict[currency], currency)

# this is a special line of code that says "Hey if run me
# directly run this code but if you import me don't"
#  - the code that runs effectively starts from here
if __name__ == '__main__':

    # if our pickle file does not exist create it using the default
    if not os.path.isfile('Currencies.pkl'):
        dump_currencies(CURRENCIES)

    print("This program allows you to check and change the currency conversion rates before using the converter program.")

    CURRENCIES = load_currencies()

    print_currencies(CURRENCIES)

    answer = input("Do you want to change an exchange rate for a currency (Y/N):")
    if answer == 'Y':
        for currency in CURRENCIES:
            # print(currency) 
            # print(type(currency)) <-- string
            print("£1 is", CURRENCIES[currency], currency)
            New_rate = float(input("Please input the new rate for "+currency+":"))
            CURRENCIES[currency] = New_rate
        dump_currencies(CURRENCIES)