[docs] [issue25701] Document that tp_setattro and tp_setattr are used for deleting attributes

[Serhiy Storchaka]

New submission from Serhiy Storchaka:

tp_setattro and tp_setattr fields of PyTypeObject are used for deleting attributes. In this case the third argument is NULL. This should be documented. Not awareness of this can cause a segmentation fail (for example see issue25698).

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assignee: docs at python
components: Documentation
messages: 255130
nosy: docs at python, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Document that tp_setattro and tp_setattr are used for deleting attributes
type: crash
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue25701>
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