Bugs item #1548371, was opened at 2006-08-29 02:27
Message generated for change (Comment added) made by rupole
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Category: None
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Roger Upole (rupole)
Assigned to: Nobody/Anonymous (nobody)
Summary: filterwarnings('error') has no effect
Initial Comment:
Once a warning has already been issued,
warnings.filterwarnings('error',...) will not cause an
error to be raised. When the attached script is run,
the warning is printed the first time thru the loop,
but no error is raised the 2nd time thru. Likewise,
warnings.filterwarnings('always',...) will not cause
the warning to be printed again.
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>Comment By: Roger Upole (rupole)
Date: 2006-09-06 05:52
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That depends on how it's expected to behave when switching
back to a filter that actually needs to check the cache.
Should 'once' mean only one time ever, or should it print
the warning again after the filters are modified ?
If the cache is cleaned up, there's no way to know if the
warning was issued prior to the modification.
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Comment By: Georg Brandl (gbrandl)
Date: 2006-09-06 01:22
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You could go another way and check/cleanup the cache on each
call to filterwarning().
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Comment By: Roger Upole (rupole)
Date: 2006-09-01 12:19
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Without the cache, the only filters you could possibly
implement would be 'error' and 'ignore'.
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Comment By: Marien Zwart (marienz)
Date: 2006-09-01 05:44
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The whole point of that cache is to not go through the list
of filters if the warning is in the cache. Why would you
keep the cache around if you search through the filters in
every case anyway?
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Comment By: Roger Upole (rupole)
Date: 2006-08-31 23:38
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It might be simpler to check if the warning is in the line
cache after the disposition is determined from the filters.
In the case of 'always' and 'error', there's no need to
check the cache at all.
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Comment By: Marien Zwart (marienz)
Date: 2006-08-31 15:34
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This is caused by the warnings module caching when a
combination of message, Warning subclass and linenumber gets
ignored and bypassing the search through the warning filters
when that same combination occurs again.
I think it is possible to avoid this problem while keeping
the cache by keeping track of the "version" of the filters
list (a simple integer that is incremented every time the
filters list is modified through the functions in the
warnings module) and including this in the key tuple
warn_explicit uses to remember previous ignores. Old stuff
would remain in the cache but that should not be a big
problem (changes to the filters list should not be that common).
Does this sound reasonable? If it does I'll see if I can
produce a patch.
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