如何在Python中实现用户定义的异常？

How can I achieve user defined exception in Python?

本问题已经有最佳答案，请猛点这里访问。

有许多内置的异常类，如EOFError、KeyboardInterrupt等。但我如何创建自己的异常类。例如，如果我想保持约束，用户应该输入长度至少为3的字符串。

您可以在类中定义异常，也可以在下面创建自己的异常类。

/ * *定义一个扩展exception的异常类* /

类Your_Exception扩展Exception:

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// redefine exception with a message
public function __construct($message, $code = 0, Exception $previous = null):

//Call Parent constructor
parent::__construct($message, $code, $previous);

// custom string representation of object
public function __to_String():
return __CLASS__ .": [{$this->code}]: {$this->message}
";

public function user_defined_Function() :
echo"user defined exception exception
";

检查此代码是否有用户定义的异常:

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class ShortInputException(Exception):
def __init__(self,length,atleast):
Exception.__init__(self)
self.length = length
self.atleast = atleast

try:
text = input('Enter some text: ')
if len(text) < 3:
raise ShortInputException(len(text),3)
except EOFError:
print('It is end of file.')
except ShortInputException as ex:
print('ShortInputException: You entered {0} length long text. Expected text size is {1}'.format(ex.length,ex.atleast))
except KeyboardInterrupt:
print('You interrupted the program execution.')
else:
print('No exception/s raised.')
print('You entered: {0}'.format(text))