Nick Coghlan <ncogh...@gmail.com> added the comment:
To get back to my original objection, it shouldn't be that difficult to
differentiate between "__context__ never set" and "__context__ explicitly
suppressed".
(e.g. using a property that sets an internal flag when set from Python code or
via PyObject_SetAttr, or else a special ExceptionContextSuppressed singleton).
BaseException could then be given a "no_context" class method that did whatever
dancing was necessary to suppress the context.
So Steven's examples would become:
def process(iterable):
try:
x = next(iterable)
except StopIteration:
raise ValueError.no_context("can't process empty iterable")
continue_processing()
def func(x):
try:
x + 0
except (ValueError, TypeError):
raise MyException.no_context('x is not a number')
do_something_with(x)
With appropriate changes to the exception display code, no_context could be as
simple as the C equivalent of the following:
@classmethod
def no_context(cls, *args, **kwds):
exc = cls(*args, **kwds)
exc.__context__ = ExceptionContextSuppressed
return exc
Another alternative would be an additional internal flag queried by the
exception chaining code itself:
@classmethod
def no_context(cls, *args, **kwds):
exc = cls(*args, **kwds)
exc.__context__ = None
exc._add_context = False
return exc
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue6210>
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