New submission from Xavier Morel <[email protected]>:
When setting `BytesWarning` programmatically (via the warnings API), though the
`warnings.filters` value matches what's obtained via `python -b` and an
explicit `warnings.warn` trigger will trigger, "native" triggers of the warning
fail to trigger properly:
import warnings
warnings.simplefilter('default', category=BytesWarning)
str(b'')
warnings.warn('test', category=BytesWarning)
If run using `python`, this will print:
test.py:4: BytesWarning: test
warnings.warn('test', category=BytesWarning)
There is no warning for the string-ification of the bytes instance.
If run using `python -b`, the behaviour is as one would expect:
test.py:3: BytesWarning: str() on a bytes instance
str(b'')
test.py:4: BytesWarning: test
warnings.warn('test', category=BytesWarning)
Inspecting `warnings.filters` shows now difference in their contents, in both
cases it is:
[('default', None, <class 'BytesWarning'>, None, 0), ('default', None,
<class 'DeprecationWarning'>, '__main__', 0), ('ignore', None, <class
'DeprecationWarning'>, None, 0), ('ignore', None, <class
'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class
'ImportWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None,
0)]
(in Python 3.9).
The warning module's own suggestion:
import sys
if not sys.warnoptions:
import warnings
warnings.simplefilter("default") # Change the filter in this process
also fails to enable BytesWarning.
If this is intended behaviour, which seems to be the case according to
ncoghlan's comment https://bugs.python.org/issue32230#msg307721, it should be
clearly documented, as it's rather frustrating.
----------
components: Library (Lib)
messages: 388912
nosy: xmorel
priority: normal
severity: normal
status: open
title: Programmatic management of BytesWarning doesn't work for native triggers.
type: behavior
versions: Python 3.6, Python 3.7, Python 3.8, Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue43526>
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