The “correct” way to define an exception in Python without PyLint complaining

Question

I\'m trying to define my own (very simple) exception class in Python 2.6, but no matter how I do it I get some warning.

First, the simplest way:

class My         


        

Answer 1

Alright, I think I figured it out. This seems to keep PyLint happy:

class MyException(Exception):
    def __init__(self, message):
        Exception.__init__(self, message)
        self.message = message

Answer 2

When you call super, you need the subclass/derived class as the first argument, not the main/base class.

From the Python online documentation:

class C(B):
    def method(self, arg):
        super(C, self).method(arg)

So your exception would be defined as follows:

class MyException(Exception):
    def __init__(self, message):
        super(MyException, self).__init__(message)
        self.message = message

Answer 3

Your first way should work. I use it myself all the time in Python 2.6.5. I don't use the "message" attribute, however; maybe that's why you're getting a runtime warning in the first example.

The following code, for example, runs without any errors or runtime warnings:

class MyException(Exception):
    pass

def thrower():
    error_value = 3
    raise MyException("My message", error_value)
    return 4

def catcher():
    try:
        print thrower()
    except MyException as (message, error_value):
        print message, "error value:", error_value

The result:

>>> catcher()
My message error value: 3

I don't know if PyLint would have a problem with the above.