[DB-SIG] PEP 249 in obsolete for Python 3000

M.-A. Lemburg mal at egenix.com
Thu Jan 29 21:47:03 CET 2009

On 2009-01-29 20:15, Vernon Cole wrote:
> I am busy hacking on code in an attempt to make adodbapi actually work in
> three environments: CPython 2.3 to 2.6, CPython 3.0, and IronPython. One of
> the first things that failed, when attempting to run on Python 3.0, was the
> test for exception definitions.  I quote:
> The module should make all error information available through
>> these exceptions or subclasses thereof:
>> Warning
>> Exception raised for important warnings like data
>> truncations while inserting, etc. It must be a subclass of
>> the Python StandardError (defined in the module
>> exceptions).
>> Error
>> Exception that is the base class of all other error
>> exceptions. You can use this to catch all errors with one
>> single 'except' statement. Warnings are not considered
>> errors and thus should not use this class as base. It must
>> be a subclass of the Python StandardError (defined in the
>> module exceptions).
> This is impossible with Python 3.0, since there is neither an "exceptions"
> module nor a "StandardError".

True, but that's render the whole PEP 249 obsolete ;-)

Mark's proposal is the correct approach for Python 3.x (and as
a matter of fact, the generally accepted way of porting apps
using StandardError to Python 3.x, AFAIK).

I'll add a note to the PEP.

> Mark Hammond provided the following workaround:
> try:
>>     from exceptions import StandardError as _BaseException
>> except ImportError:
>>     # py3k
>>     _BaseException = Exception
>> class Error(_BaseException):
>>     pass
>> class Warning(_BaseException):
>>     pass
> This makes the code work fine, except that, by strict definition, it
> violates the api.

Marc-Andre Lemburg

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