[issue40815] Multiprocessing docs don't describe thread-safety
Change by Alan Briolat : -- nosy: +alan.briolat ___ Python tracker <https://bugs.python.org/issue40815> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21172] Unexpected behaviour with logging.LogRecord "first arg is dict" case
New submission from Alan Briolat: The logging.LogRecord class is more restrictive with its "first arg is dict" case than the formatting operator it uses requires. As far as I can tell, for "%(foo)s" % bar, the minimum contract is that bar.__getitem__("foo") succeeds, not that bar is an instance of dict. However, fulfilling only this minimum contract results in LogRecord raising an exception at the point of applying the string format, which is confusing considering the "same" expression succeeds outside of logging. See the attached file for how 2 "equivalent" expressions behave completely differently. For resolution, I wonder if checking for "hasattr(..., '__getitem__')" instead of "isinstance(..., dict)" would be sufficient? -- components: Library (Lib) files: logging_format_bug.py messages: 215713 nosy: alan.briolat priority: normal severity: normal status: open title: Unexpected behaviour with logging.LogRecord "first arg is dict" case type: behavior versions: Python 2.7, Python 3.1, Python 3.2, Python 3.3, Python 3.4, Python 3.5 Added file: http://bugs.python.org/file34750/logging_format_bug.py ___ Python tracker <http://bugs.python.org/issue21172> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21172] Unexpected behaviour with logging.LogRecord "first arg is dict" case
Alan Briolat added the comment: Because the object in question is not actually a dict, LogRecord is attempting, in this example, "%(bar)s" % (f,) instead of "%(bar)s" % f. In unicodeobject.c this causes the PyMapping_Check in PyUnicode_Format to fail because it's a tuple (note that PyMapping_Check *only* checks for the __getitem__ attribute), the argument to not be treated as a dict, and consequently ctx.dict = NULL for the format operation. This condition, combined with still attempting to resolve named values in the format string, causes unicode_format_arg_parse to raise the TypeError("format requires a mapping"). Speaking of documentation, the language of https://docs.python.org/2/library/logging.html#logging.Logger.debug strongly suggests that logging.debug(msg, args...) should be considered equivalent to logging.debug(msg % args...), which still means this is still "unexpected" behaviour. The intention is clearly to allow this special case to pass through to the formatting operator unimpeded, however this doesn't happen. Also, even if "the mapping protocol" should remain the key concept (the behaviour of PyMapping_Check being a happy accident), checking for isinstance(..., dict) is still wrong - it should at least be collections.Mapping to give users a chance to emulate the correct interface. -- status: pending -> open ___ Python tracker <http://bugs.python.org/issue21172> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com