[Python-Dev] What's New text on future maintenance (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Fri May 7 11:52:49 CEST 2010

Terry Reedy wrote:

Then the warnings stuff

* Because 2.7 will be running production applications, a policy Every major version (xcept 3.0) has run production application, and 3.1 may be and 3.2 certainly will be. So this reasoning is not clear to me. decision was made to silence warnings only of interest to developers by default. I believe this is meant to say "Warnings aimed only at those porting code to 3.x are silenced by default."

Actually, the decision was indeed to make all Deprecation Warnings silent by default. The rationale was a bit different from what AMK currently has though (otherwise we wouldn't have made the same change in 3.x). I'll take a stab at a more accurate rationale:

"""For previous releases, it has been the policy of the CPython core developers that :exc:DeprecationWarning should be enabled by default. This provides Python developers with a clear indication when their code has a substantial risk of breaking in the next major version of Python. However, the nature of Python usage has changed over the years, such that there are now a significantly larger number of Python application users that are not directly involved in the development of those applications. This has lead to a situation where users may be receiving irrelevant warnings from an application that is actually working correctly, creating unnecessary concern for affected end users and additional overhead for the developers of these applications in responding to these concerns.

Accordingly, starting with Python 2.7, this policy has been revised and the CPython interpreter has been updated to silence all occurrences of :exc:DeprecationWarning by default. Developers wishing to see if their application is at significant risk of breaking on the next major Python release can re-enable display of :exc:DeprecationWarning messages by running Python with the :option:-Wdefault (short form: :option:-Wd) switch, or you can add warnings.simplefilter('default') to your code. (Note that the 'default' in these settings refers to the default warning behaviour of displaying warnings once for each location where they are encountered rather than to the overall default warning settings used by the interpreter)"""

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

More information about the Python-Dev mailing list