Beginning Python: Exceptions, Errors, and Warnings

From Al Lukaszewski, former About.com Guide

But what if you do not want to give the user something obtuse like NameError or IOError. Python also provides a way to present customised error messages by using the built-in class Exception. To use it, simply plug "Exception" as the argument of raise.

 >>> raise Exception 
 Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
 Exception 

"Where is the error message?" Well, I wanted you to see that you could raise a simple error by not giving any further arguments than "Exception". If you want to print something beyond this, enclose your message in quotes and separate it from "Exception" by a comma:

 >>> raise Exception, "This is my customised error message." 
 Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
 Exception: This is my customised error message. 

That summarises Python's exceptions, if you would like a list of them, you will find a page each of Python's exceptions and warnings in the section on the Python Library.

Other tutorials in this series: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8

Previous

• What is an Exception?
• Exception Exemplified
• If at First You Don't Succeed
• Try, Try Again
• Taking Exception
• If All Else Fails...
• Raising Your Own Exceptions With raise - Part 1
• Raising Your Own Exceptions With raise - Part 2

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