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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 MyException(Exception): pass
This works, but prints out a warning at runtime: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6 OK, so that’s not the way. I then tried:
class MyException(Exception): def __init__(self, message): self.message = message
This also works, but PyLint reports a warning:
W0231: MyException.__init__: __init__ method from base class 'Exception' is not called. So I tried calling it:
class MyException(Exception): def __init__(self, message): super(Exception, self).__init__(message) self.message = message
This works, too! But now PyLint reports an error:
E1003: MyException.__init__: Bad first argument 'Exception' given to super class
How the hell do I do such a simple thing without any warnings?
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
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
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
>>> catcher() My message error value: 3
I don’t know if PyLint would have a problem with the above.