Python输入验证函数保留旧变量

Question

我目前正在编写一个税收计算器，我注意到如果我输入了一个无效的税收代码，一开始它看起来会被拒绝，但随后程序似乎保留了初始输入并以相反的顺序循环它们（像这样）：

[User Input] Gross Income: £32,000
[User Input] Tax Code: 32,000
Tax Code after input: 32,000
Failed letter check
Invalid input. Please enter your tax code.
[User Input] Tax Code: y      
Tax Code after input: y
Passed letter check
Tax Code after letter check: y
Tax Code during dictionary match check (false): y
Failed dictionary match check
Invalid input. Please enter your tax code.       
[User Input] Tax Code: 1257L  
Tax Code after input: 1257L
Passed letter check
Tax Code after letter check: 1257L
Tax Code during dictionary match check (true): 1257L
Passed dictionary match check
Tax Code after dictionary match check: 1257L
Personal Allowance: 12570
Tax Letter: L
Tax Code after dictionary match check: y
Personal Allowance: 0
Tax Letter: Y
Tax Code after letter check: 32,000
Traceback (most recent call last):
  File "C:\Users\Joshua.Riberio\Git\taxcalc\taxcalc.py", line 336, in <module>   
    salarycalc()
  File "C:\Users\Joshua.Riberio\Git\taxcalc\taxcalc.py", line 243, in salarycalc 
    personal_allowance, tax_letter = get_tax_code()
  File "C:\Users\Joshua.Riberio\Git\taxcalc\taxcalc.py", line 78, in get_tax_code
    tax_letter = tax_code[tax_letter_index:].upper()
TypeError: slice indices must be integers or None or have an __index__ method

这是我的代码：

def get_tax_code():
    tax_code = input('Tax Code: ')
    print('Tax Code after input:', tax_code)
    tax_letter_index = ''
    # Checking input contains a letter
    for char in tax_code:
        if char.upper() in alpha:
            tax_letter_index = tax_code.index(char)
            print('Passed letter check')
            break
    
    if tax_letter_index == '':
        print('Failed letter check')
        print('Invalid input. Please enter your tax code.')
        get_tax_code()

    print('Tax Code after letter check:', tax_code)

    tax_letter = tax_code[tax_letter_index:].upper()

    # Checking input has a key match in the tax_letters dictionary
    if tax_letter not in tax_letters.keys():
        print('Tax Code during dictionary match check (false):', tax_code)
        print('Failed dictionary match check')
        print('Invalid input. Please enter your tax code.')
        get_tax_code()
    elif tax_letter in tax_letters.keys():
        print('Tax Code during dictionary match check (true):', tax_code)
        print('Passed dictionary match check')
        
    print('Tax Code after dictionary match check:', tax_code)

    # Getting personal allowance from Tax Code
    personal_allowance = tax_code[:tax_letter_index]
    if personal_allowance == '':
        personal_allowance = 0
    else:
        personal_allowance = int(personal_allowance) * 10

    # Setting personal allowance exceptions for gross income over £100,000
    if gross_income > 100000:
        personal_allowance = set_personal_allowance - ((gross_income - 100000) / 2)
        if personal_allowance < 0:
            personal_allowance = 0
            
    print('Personal Allowance:', personal_allowance)
    print('Tax Letter:', tax_letter)
    
    return personal_allowance, tax_letter

过多的打印只是为了让我可以看到输入的更改位置。似乎在成功运行后，代码使用先前的无效输入循环回到顶部，导致代码无法运行。

谁能看出我哪里出错了？

备注

tax_letters 是一个已定义的字典，将对其进行更新以从选定的 CSV 中提取：

tax_letters = {
    "L": "You’re entitled to the standard tax-free Personal Allowance",
    "M": "Marriage Allowance: you’ve received a transfer of 10% of your partner’s Personal Allowance",
    "N": "Marriage Allowance: you’ve transferred 10% of your Personal Allowance to your partner",
    "T": "Your tax code includes other calculations to work out your Personal Allowance",
    "0T": "Your Personal Allowance has been used up, or you’ve started a new job and your employer does not have the details they need to give you a tax code",
    "BR": "All your income from this job or pension is taxed at the basic rate (usually used if you’ve got more than one job or pension)",
    "D0": "All your income from this job or pension is taxed at the higher rate (usually used if you’ve got more than one job or pension)",
    "D1": "All your income from this job or pension is taxed at the additional rate (usually used if you’ve got more than one job or pension)",
    "NT": "You’re not paying any tax on this income",
    "S": "Your income or pension is taxed using the rates in Scotland",
    "S0T": "Your Personal Allowance (Scotland) has been used up, or you’ve started a new job and your employer does not have the details they need to give you a tax code",
    "SBR": "All your income from this job or pension is taxed at the basic rate in Scotland (usually used if you’ve got more than one job or pension)",
    "SD0": "All your income from this job or pension is taxed at the intermediate rate in Scotland (usually used if you’ve got more than one job or pension)",
    "SD1": "All your income from this job or pension is taxed at the higher rate in Scotland (usually used if you’ve got more than one job or pension)",
    "SD2": "All your income from this job or pension is taxed at the top rate in Scotland (usually used if you’ve got more than one job or pension)",
    "C": "Your income or pension is taxed using the rates in Wales",
    "C0T": "Your Personal Allowance (Wales) has been used up, or you’ve started a new job and your employer does not have the details they need to give you a tax code",
    "CBR": "All your income from this job or pension is taxed at the basic rate in Wales (usually used if you’ve got more than one job or pension)",
    "CD0": "All your income from this job or pension is taxed at the higher rate in Wales (usually used if you’ve got more than one job or pension)",
    "CD1": "All your income from this job or pension is taxed at the additional rate in Wales (usually used if you’ve got more than one job or pension)"
    }

gross_income在main函数中定义：

def salarycalc():
    screen_clear()

    global gross_income
    gross_income = input('Gross Income: £')

    if ',' in gross_income:
        gross_income = gross_income.replace(',', '')

    if '£' in gross_income:
        gross_income = gross_income.replace('£', '')

    gross_income = float(gross_income)

set_personal_allowance 是由 'tax_brackets' 字典中的值定义的变量，稍后将再次更新它以从 CSV 的选择中提取：

tax_brackets = {
    'Personal Allowance': 12570,
    'Basic': [0, 0.2],
    'Higher': [50270, 0.4],
    'Additional': [150000, 0.45]
}

set_personal_allowance = tax_brackets['Personal Allowance']

Answer 1

因此，您的代码可能无法正常工作的主要原因是重复的递归调用。为了使方法更简单，我将所需的功能分解为 2 个验证检查。请注意，我已经包含了一些示例数据来检查程序，您可以相应地忽略它。
只要两个检查为真，驱动程序函数get_tax_code 就会运行，这意味着只有在通过字母检查和字典匹配验证税码后，它才会停止询问输入。

def get_tax_code(tax_letters):
    gross_income = 32000
    set_personal_allowance = 12570
    check1 = True
    check2 = True

    while check1 or check2:
        tax_code = input('Tax Code: ')
        print('Tax Code after input:', tax_code)
        tax_letter_index = verify1(tax_code)
        if tax_letter_index != -1:
            check1 = False
            tax_letter = tax_code[tax_letter_index:].upper()
            print('Tax Code after letter check:', tax_code)
            x = verify2(tax_letter, tax_letters)
            if x:
                print('Tax Code during dictionary match check (true):', tax_code)
                print('Passed dictionary match check')
                print('Tax Code after dictionary match check:', tax_code)
                check2 = False
            else:
                print('Tax Code during dictionary match check (false):', tax_code)
                print('Failed dictionary match check')
                print('Invalid input. Please enter your tax code.')
        
        else:
            print('Failed letter check')
            print('Invalid input. Please enter your tax code.')

    
    # Getting personal allowance from Tax Code
    personal_allowance = tax_code[:tax_letter_index]
    if personal_allowance == '':
        personal_allowance = 0
    else:
        personal_allowance = int(personal_allowance) * 10

    # Setting personal allowance exceptions for gross income over £100,000
    if gross_income > 100000:
        personal_allowance = set_personal_allowance - ((gross_income - 100000) / 2)
        if personal_allowance < 0:
            personal_allowance = 0
            
    print('Personal Allowance:', personal_allowance)
    print('Tax Letter:', tax_letter)

这些是早先包含在get_tax_code 中的两个辅助函数。
第一个函数 verify1() 负责字母检查，而第二个函数 verify2()handles 字典匹配。这两个函数返回的值决定了检查值是否被更新，进而决定用户是否必须再次提供tax_code 输入。

def verify1(tax_code):
    tax_letter_index = ''
    # Checking input contains a letter
    for char in tax_code:
        if char.upper().isalpha():
            tax_letter_index = tax_code.index(char)
            print('Passed letter check')
            break
    if tax_letter_index == '':
        return -1
    else:
        return tax_letter_index

def verify2(tax_letter, tax_letters):
    if tax_letter not in tax_letters.keys():
        return False
    elif tax_letter in tax_letters.keys():
        return True

输出

Tax Code: 3200
Tax Code after input: 3200
Failed letter check
Invalid input. Please enter your tax code.
Tax Code: y
Tax Code after input: y
Passed letter check
Tax Code during dictionary match check (false): y
Failed dictionary match check
Invalid input. Please enter your tax code.
Tax Code: 1257L
Tax Code after input: 1257L
Passed letter check
Tax Code during dictionary match check (true): 1257L
Passed dictionary match check
Tax Code after dictionary match check: 1257L
Personal Allowance: 12570
Tax Letter: L