You are looking for the bug fix http://bugs.python.org/issue4180:
"warnings.simplefilter("always") does not make warnings always show up" Python 2.7 has a bug, Python 3.4.3+ behaves correctly. It is surprising that Python 3.4.0 and Python 3.4.3 behaves differently :-) (Ubuntu 14.04 uses Python 3.4.0.. Victor 2016-11-14 14:58 GMT+01:00 Christoph Groth <christ...@grothesque.org>: > (I assume that this list is appropriate for this topic, but if it isn't, I > will be grateful for being redirected to the appropriate place.) > > It seems that warnings behave differently in Python 2 and Python 3. > Consider the following script. > > **************** > def func(): > warnings.warn("Blabla", RuntimeWarning) > > warnings.simplefilter("ignore") > func() > warnings.simplefilter("always") > func() > **************** > > When run with CPython 2.7, there is no output, when run with CPython 3.5, > there is the following output: > > **************** > /tmp/test.py:4: RuntimeWarning: Blabla > warnings.warn("Blabla", RuntimeWarning) > **************** > > Was there indeed a change of how warnings behave in Python 3? I searched, > but couldn't find any documentation for this. > > Understanding how warnings work is especially important when testing for > them. > This is how I stumbled across this, in case anyone is interested: > https://gitlab.kwant-project.org/kwant/kwant/issues/1#note_2608 > > I also note that the current documentation still uses DeprecationWarning in > the example of how to suppress a warning: > https://docs.python.org/dev/library/warnings.html#temporarily-suppressing-warnings. > Since DeprecationWarning is disabled by default in modern Python, perhaps a > different warning would provide a better example? > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/victor.stinner%40gmail.com _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com