Section 10.5. Exceptions as Strings

10.5. *Exceptions as Strings

Prior to Python 1.5, standard exceptions were implemented as strings. However, this became limiting in that it did not allow for exceptions to have relationships to each other. With the advent of exception classes, this is no longer the case. As of 1.5, all standard exceptions are now classes. It is still possible for programmers to generate their own exceptions as strings, but we recommend using exception classes from now on.

For backward compatibility, it is possible to revert to string-based exceptions. Starting the Python interpreter with the command-line option -Xwill provide you with the standard exceptions as strings. This feature will be obsolete beginning with Python 1.6.

Python 2.5 begins the process of deprecating string exceptions from Python forever. In 2.5, raise of string exceptions generates a warning. In 2.6, the catching of string exceptions results in a warning. Since they are rarely used and are being deprecated, we will no longer consider string exceptions within the scope of this book and have removed it. (You may find the original text in prior editions of this book.) The only point of relevance and the final thought is a caution: You may use an external or third-party module, which may still have string exceptions. String exceptions are a bad idea anyway. One reader vividly recalls seeing Linux RPM exceptions with spelling errors in the exception text.