python-3.x - 如何在不将错误处理写入函数的情况下创建自定义错误处理类

Question

我正在尝试创建一个只处理错误的类。在调用函数时使用类方法，以便错误处理类中的方法在用户输入错误时停止函数的执行。

class Error(Exception):
    pass

class UserError(Error):
    def handle_even(number):
        try: number % 2 == 0    
        except: raise UserError.handle_even('error: odd number\n')
    def handle_odd(number):
        try: number % 2 != 0
        except: raise UserError.handle_odd('error: even number\n')


def take_even(number):
    print(number) #if user input is bad, this shouldn't execute

def take_odd(number):
    print(number) #if user input is bad, this shouldn't execute



take_even(UserError.handle_even(5)) # I expect this to print 'error: odd number'
take_odd(UserError.handle_odd(4)) # I expect this to print 'error: even number'

所以，我想要的输出是:

error: odd number
error: even number

但是，我得到的输出是:

None
None

Answer 1

try block 不会产生异常，因为表达式评估是真/假，而且您的奇数/偶数检查逻辑是错误的。

class Error(Exception):
    pass

class UserError(Error):
    @classmethod
    def handle_even(cls, number):
        if number % 2 != 0:
            raise Error('error: odd number\n')

        return number

    @classmethod
    def handle_odd(cls, number):
        if number % 2 == 0:
            raise Error('error: even number\n')

        return number


def take_even(number):
    print(number) # if user input is bad, this won't execute

def take_odd(number):
    print(number) # if user input is bad, this won't execute

# This will raise an 'Error' exception (error: odd number)
take_even(UserError.handle_even(5))

# This will raise an 'Error' exception (error: even number)
take_odd(UserError.handle_odd(4))

您可以像这样处理这些特定的Error 异常:

try:
    take_even(UserError.handle_even(5))
except Error as e:
    print(e) # print 'error: odd number'

try:
    take_odd(UserError.handle_odd(4))
except Error as e:
    print(e) # print 'error: even number'

编辑:根据@NathanVērzemnieks 的建议将方法更改为类方法。