New submission from Thomas Robitaille:
In Python 3.5, the following code:
import warnings
def deal_with_warning(*args, **kwargs):
print("warning emitted")
with warnings.catch_warnings(record=True):
warnings.showwarning = deal_with_warning
warnings.warn("This is a warning")
results in "warning emitted" being printed to the terminal.
In Python 3.6 however (at least in 3.6b1), nothing is printed, meaning that
``deal_with_warning`` is not getting called. I bisected the CPython history and
tracked it down to the changes in this issue:
https://bugs.python.org/issue26568
However it doesn't look like this was an intentional change in behavior, since
it says in the description of that issue:
"For backward compatibility, warnings.showmsg() calls warnings.showwarning() if
warnings.showwarning() was replaced. Same for warnings.formatmsg(): call
warnings.formatwarning() if replaced."
So I believe this is a bug? (since backward-compatibility is not preserved). If
not, should the change in behavior be mentioned in the changelog?
----------
messages: 282056
nosy: Thomas.Robitaille
priority: normal
severity: normal
status: open
title: Change in behavior when overriding warnings.showwarning and with
catch_warnings(record=True)
versions: Python 3.6
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Python tracker <[email protected]>
<http://bugs.python.org/issue28835>
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