[Python-Dev] "-Wd" switch

Larry Hastings larry at hastings.org
Tue Apr 6 13:19:55 CEST 2010

Jesus Cea wrote:
> Recently we added "-Wd" flags to buildbots. I was wondering about the
> effect of it. documentation doesn't help.
> I could study the code, but I guess other people can have the very same
> question and I think the answer should be in the archives, somewhere.

I studied the code ;)

-Wd enables all warnings.  It adds 'd' to sys.warnoptions, which in turn 
adds a new first entry to _warnings.filters which matches all warnings 
and enables the "default" behavior, which is to show it once per 
execution of the Python interpreter.

For example, if you run "python -Wd" on the current trunk (2.7) and 
execute the statement "import bsddb" you get a PendingDeprecationWarning 
exception.  Without -Wd that warning would be suppressed.

Hope I didn't miss any important subtleties,


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