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Clarify execution order in init #488

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merged 5 commits into from
Feb 9, 2019
Merged

Clarify execution order in init #488

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a09ea0e
Clarify execution order in init
hynek Jan 22, 2019
7fb18bc
Clarify attributes are processed in the order of declaration
hynek Jan 23, 2019
8861a32
Simple past is good enough
hynek Jan 23, 2019
dbfa392
Merge branch 'master' into validators-order
hynek Feb 1, 2019
374d991
Merge branch 'master' into validators-order
hynek Feb 8, 2019
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17 changes: 17 additions & 0 deletions docs/init.rst
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Expand Up @@ -350,6 +350,23 @@ If you need to set attributes on a frozen class, you'll have to resort to the :r

Note that you *must not* access the hash code of the object in ``__attrs_post__init__`` if ``cache_hash=True``.


Order of Execution
------------------

If present, the hooks are executed in the following order:

1. For each attribute, in the order it was declared:

a. default factory
b. converter

2. *all* validators
3. ``__attrs_post_init__``

Notably this means, that you can access all attributes from within your validators, but your converters have to deal with invalid values and have to return a valid value.


.. _`Wiki page`: https://github.com/python-attrs/attrs/wiki/Extensions-to-attrs
.. _`get confused`: https://github.com/python-attrs/attrs/issues/289
.. _`there is no such thing as a private argument`: https://github.com/hynek/characteristic/issues/6