[Python-Dev] Py3k DeprecationWarning in stdlib
andrew-pythondev at puzzling.org
Wed Jun 25 15:08:57 CEST 2008
Nick Coghlan wrote:
> I forgot this had already been added to the Python regression test
> machinery, so it will just be a matter of updating the relevant tests to
> use it:
That's a nice surprise! I'm glad the standard library is growing facilities
I think it could be improved a little, though:
> Return a context manager that guards the warnings filter from being
> permanently changed and records the data of the last warning that has
> been issued. The record argument specifies whether any raised warnings
> are captured by the object returned by warnings.catch_warning() or
> allowed to propagate as normal.
The description doesn't really make the record=False case clear. This context
manager is doing two different jobs: 1) restore the filters list and showwarning
function to their original state when done, and 2) optionally (if record=True)
record the last warning in the "as" target. That feels a bit weird.
I think a clearer way to provide that functionality would be with two separate
context managers: one that copies and finally restores the filters list and
showwarnning function called protect_warnings_module, and then catch_warnings to
record the warnings. The catch_warnings context manager could reuse the
protect_warnings_module one. "with protect_warnings_module:" seems easier to
understand (and document) than "with catch_warning(record=False)".
Should I file a bug for this?
> The context manager is typically used like this:
> with catch_warning() as w:
> assert str(w.message) == "foo"
Maybe this is a YAGNI, but what if an expression triggers multiple warnings?
Perhaps the WarningMessage object ought to keep a list rather than just the last
Another thought: if the warnings module had a public, documented way to
manipulate the filter list (e.g. warnings.get_all_filters() and
warnings.set_all_filters(...)), then people could build these sorts of test
facilities for themselves if the test_support one turns out to be too limiting
or otherwise a poor fit.
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