Re: [Python-Dev] peps: New PEP 490: Chain exceptions at C level
On 26.03.15 10:08, victor.stinner wrote:
https://hg.python.org/peps/rev/7daf3bfd9586 changeset: 5741:7daf3bfd9586 user: Victor Stinner victor.stinner@gmail.com date: Thu Mar 26 09:08:08 2015 +0100 summary: New PEP 490: Chain exceptions at C level
+Python 3.5 introduces a new private ``_PyErr_ChainExceptions()`` function which +is enough to chain manually exceptions.
It also was added in Python 3.4.3.
I meditar about adding _PyErr_ReplaceException() in 2.7 for simpler backporting patches from 3.x.
+Functions like ``PyErr_SetString()`` don't chain automatically exceptions. To +make usage of ``_PyErr_ChainExceptions()`` easier, new functions are added:
+* PyErr_SetStringChain(exc_type, message) +* PyErr_FormatChaine(exc_type, format, ...)
Typo.
+* PyErr_SetNoneChain(exc_type) +* PyErr_SetObjectChain(exc_type, exc_value)
I would first make these functions private, as _PyErr_ChainExceptions(). After proofing their usefulness in the stdlib, they can be made public.
There is another issue: exception chain is not set up on exception creation in python code, only on throwing. Thus I have to assign `__context__` and `__cause__` attributes manually if I want to call `future.set_exception(exc)` instead of `raise exc`.
See aiohttp code for usage example: https://github.com/KeepSafe/aiohttp/blob/931efbd518d0d99522d1cd36b43620657cd...
On Thu, Mar 26, 2015 at 11:11 AM, Serhiy Storchaka storchaka@gmail.com wrote:
On 26.03.15 10:08, victor.stinner wrote:
https://hg.python.org/peps/rev/7daf3bfd9586 changeset: 5741:7daf3bfd9586 user: Victor Stinner victor.stinner@gmail.com date: Thu Mar 26 09:08:08 2015 +0100 summary: New PEP 490: Chain exceptions at C level
+Python 3.5 introduces a new private ``_PyErr_ChainExceptions()`` function which +is enough to chain manually exceptions.
It also was added in Python 3.4.3.
I meditar about adding _PyErr_ReplaceException() in 2.7 for simpler backporting patches from 3.x.
+Functions like ``PyErr_SetString()`` don't chain automatically exceptions. To +make usage of ``_PyErr_ChainExceptions()`` easier, new functions are added:
+* PyErr_SetStringChain(exc_type, message) +* PyErr_FormatChaine(exc_type, format, ...)
Typo.
+* PyErr_SetNoneChain(exc_type) +* PyErr_SetObjectChain(exc_type, exc_value)
I would first make these functions private, as _PyErr_ChainExceptions(). After proofing their usefulness in the stdlib, they can be made public.
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2015-03-26 11:52 GMT+01:00 Andrew Svetlov andrew.svetlov@gmail.com:
There is another issue: exception chain is not set up on exception creation in python code, only on throwing.
I'm not suprised of that.
Thus I have to assign `__context__` and `__cause__` attributes manually if I want to call `future.set_exception(exc)` instead of `raise exc`.
Do you mean that we need an helper to make this task even simpler? Or do you suggest to set them automatically in the constructor?
Victor
I think setting context in exception constructor would be fine.
On Thu, Mar 26, 2015 at 1:36 PM, Victor Stinner victor.stinner@gmail.com wrote:
2015-03-26 11:52 GMT+01:00 Andrew Svetlov andrew.svetlov@gmail.com:
There is another issue: exception chain is not set up on exception creation in python code, only on throwing.
I'm not suprised of that.
Thus I have to assign `__context__` and `__cause__` attributes manually if I want to call `future.set_exception(exc)` instead of `raise exc`.
Do you mean that we need an helper to make this task even simpler? Or do you suggest to set them automatically in the constructor?
Victor
Thanks Serhiy for your review, I modified the PEP. I just sent a first draft (including your suggestions) to python-dev.
Victor
participants (3)
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Andrew Svetlov -
Serhiy Storchaka -
Victor Stinner