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[RFC] PEP 526: class member annotations in 3.6 #214

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hynek opened this issue Jun 24, 2017 · 7 comments
Closed

[RFC] PEP 526: class member annotations in 3.6 #214

hynek opened this issue Jun 24, 2017 · 7 comments
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@hynek
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@hynek hynek commented Jun 24, 2017

I just played around and got:

>>> import attr

>>> @attr.s
... class C:
...     x: int
...     y: int = attr.ib(default=42)

>>> C(1)
C(x=1, y=42)

>>> C("1", 23)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<attrs generated init 057634913447d4e148358419a9dd355e479f9105>", line 5, in __init__
    __attr_validator_x(self, __attr_x, self.x)
  File "/Users/hynek/Projects/attrs/src/attr/validators.py", line 33, in __call__
    attr, self.type, value,
TypeError: ("'x' must be <class 'int'> (got '1' that is a <class 'str'>).", Attribute(name='x', default=NOTHING, validator=<instance_of validator for type <class 'int'>>, repr=True, cmp=True, hash=None, init=True, convert=None, metadata=mappingproxy({})), <class 'int'>, '1')
("'x' must be <class 'int'> (got '1' that is a <class 'str'>).", Attribute(name='x', default=NOTHING, validator=<instance_of validator for type <class 'int'>>, repr=True, cmp=True, hash=None, init=True, convert=None, metadata=mappingproxy({})), <class 'int'>, '1')

working within five minutes (biggest “challenge” was to ignore the counter on _CountingAttr).

I think this is really neat because it saves us from fiddling with the class body and makes much more sense conceptually.


Now, obviously we can’t just start harvesting class annotations, we need an option or even a new decorator.

I also see this as a chance to get rid of the slots/non-slots dichotomy that fell a few times on our feet and always go the slots way (= create new class).

So I hereby ask for:

  • feedback/opinions
  • suggestions for decorator/option name
  • other warts we could fix while doing this
@hynek hynek added the Feature label Jun 24, 2017
@hynek hynek changed the title [RFC] 3.6 class annotations [RFC] PEP 526: class member annotations in 3.6 Jun 26, 2017
@glyph
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@glyph glyph commented Jun 26, 2017

Over on ericvsmith/dataclasses#19 Guido made a very good point; if we want the type checker to work, the type field needs to have nothing but a type in it. So: x: int, but y = attr.ib(); possibly y: int = attr.ib().

@hynek
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@hynek hynek commented Jun 26, 2017

(thanks, I’ve updated the comment so people don’t see the wrong version first thing)

@glyph
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@glyph glyph commented Jun 26, 2017

Cool! I take it you got that working as well, without issue :)

@jmcs
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@jmcs jmcs commented Jun 29, 2017

y: int = attr.ib() doesn't work well with pylint (pylint will use the type of ib not int). For the common use case of setting a default I would like something like:

>>> import attr

>>> @attr.s
... class C:
...     x: int
...     y: int = 42

>>> C(1)
C(x=1, y=42)
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@glyph glyph commented Jul 1, 2017

y: int = attr.ib() doesn't work well with pylint (pylint will use the type of ib not int).

IMHO the solution here is to fix pylint; it's just doing the wrong thing. This idea of defaults = cvars seems like a good idea until (as the participants in the dataclasses repo did) you realize that you will almost immediately want

x: list = []

and now nothing makes sense any more. If you do

x: list = new(list)

it's still the wrong type.

@hynek
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@hynek hynek commented Jul 3, 2017

FTR, I consider #215 a prerequisite for working on this. In the end, this is just syntactic sugar for it.

@hynek
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@hynek hynek commented Sep 26, 2017

PEP 526 support has been merged in #239!

@hynek hynek closed this Sep 26, 2017
bors-fusion bot added a commit to fusionapp/fusion-index that referenced this issue Nov 15, 2017
Merge #167
167: Scheduled weekly dependency update for week 46 r=mithrandi




## Updates
Here's a list of all the updates bundled in this pull request. I've added some links to make it easier for you to find all the information you need.
<table align="center">

<tr>
<td><b>attrs</b></td>
<td align="center">17.2.0</td>
<td align="center">&raquo;</td>
<td align="center">17.3.0</td>
<td>
     <a href="https://pypi.python.org/pypi/attrs">PyPI</a> | <a href="https://pyup.io/changelogs/attrs/">Changelog</a> | <a href="http://www.attrs.org/">Homepage</a> 

</td>

<tr>
<td><b>cryptography</b></td>
<td align="center">2.1.2</td>
<td align="center">&raquo;</td>
<td align="center">2.1.3</td>
<td>
     <a href="https://pypi.python.org/pypi/cryptography">PyPI</a> | <a href="https://pyup.io/changelogs/cryptography/">Changelog</a> | <a href="https://github.com/pyca/cryptography">Repo</a> 

</td>

<tr>
<td><b>hypothesis</b></td>
<td align="center">3.33.0</td>
<td align="center">&raquo;</td>
<td align="center">3.37.0</td>
<td>
     <a href="https://pypi.python.org/pypi/hypothesis">PyPI</a> | <a href="https://pyup.io/changelogs/hypothesis/">Changelog</a> | <a href="https://github.com/HypothesisWorks/hypothesis/issues">Repo</a> 

</td>

</tr>
</table>



## Changelogs


### attrs 17.2.0 -> 17.3.0

>### 17.3.0

>-------------------

>Backward-incompatible Changes
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>- Attributes are not defined on the class body anymore.

>  This means that if you define a class ``C`` with an attribute ``x``, the class will *not* have an attribute ``x`` for introspection anymore.
>  Instead of ``C.x``, use ``attr.fields(C).x`` or look at ``C.__attrs_attrs__``.
>  The old behavior has been deprecated since version 16.1.
>  (`253 &lt;https://github.com/python-attrs/attrs/issues/253&gt;`_)


>Changes
>^^^^^^^

>- ``super()`` and ``__class__`` now work on Python 3 when ``slots=True``.
>  (`102 &lt;https://github.com/python-attrs/attrs/issues/102&gt;`_, `226 &lt;https://github.com/python-attrs/attrs/issues/226&gt;`_, `269 &lt;https://github.com/python-attrs/attrs/issues/269&gt;`_, `270 &lt;https://github.com/python-attrs/attrs/issues/270&gt;`_, `272 &lt;https://github.com/python-attrs/attrs/issues/272&gt;`_)
>- Added ``type`` argument to ``attr.ib()`` and corresponding ``type`` attribute to ``attr.Attribute``.

>  This change paves the way for automatic type checking and serialization (though as of this release ``attrs`` does not make use of it).
>  In Python 3.6 or higher, the value of ``attr.Attribute.type`` can alternately be set using variable type annotations
>  (see `PEP 526 &lt;https://www.python.org/dev/peps/pep-0526/&gt;`_). (`151 &lt;https://github.com/python-attrs/attrs/issues/151&gt;`_, `214 &lt;https://github.com/python-attrs/attrs/issues/214&gt;`_, `215 &lt;https://github.com/python-attrs/attrs/issues/215&gt;`_, `239 &lt;https://github.com/python-attrs/attrs/issues/239&gt;`_)
>- The combination of ``str=True`` and ``slots=True`` now works on Python 2.
>  (`198 &lt;https://github.com/python-attrs/attrs/issues/198&gt;`_)
>- ``attr.Factory`` is hashable again. (`204
>  &lt;https://github.com/python-attrs/attrs/issues/204&gt;`_)
>- Subclasses now can overwrite attribute definitions of their superclass.

>  That means that you can -- for example -- change the default value for an attribute by redefining it.
>  (`221 &lt;https://github.com/python-attrs/attrs/issues/221&gt;`_, `229 &lt;https://github.com/python-attrs/attrs/issues/229&gt;`_)
>- Added new option ``auto_attribs`` to ``attr.s`` that allows to collect annotated fields without setting them to ``attr.ib()``.

>  Setting a field to an ``attr.ib()`` is still possible to supply options like validators.
>  Setting it to any other value is treated like it was passed as ``attr.ib(default=value)`` -- passing an instance of ``attr.Factory`` also works as expected.
>  (`262 &lt;https://github.com/python-attrs/attrs/issues/262&gt;`_, `277 &lt;https://github.com/python-attrs/attrs/issues/277&gt;`_)
>- Instances of classes created using ``attr.make_class()`` can now be pickled.
>  (`282 &lt;https://github.com/python-attrs/attrs/issues/282&gt;`_)


>----








### hypothesis 3.33.0 -> 3.37.0

>### 3.37.0

>-------------------

>This is a deprecation release for some health check related features.

>The following are now deprecated:

>* Passing :attr:`~hypothesis.HealthCheck.exception_in_generation` to
>  :attr:`~hypothesis.settings.suppress_health_check`. This no longer does
>  anything even when passed -  All errors that occur during data generation
>  will now be immediately reraised rather than going through the health check
>  mechanism.
>* Passing :attr:`~hypothesis.HealthCheck.random_module` to
>  :attr:`~hypothesis.settings.suppress_health_check`. This hasn&#39;t done anything
>  for a long time, but was never explicitly deprecated. Hypothesis always seeds
>  the random module when running given tests, so this is no longer an error
>  and suppressing it doesn&#39;t do anything.
>* Passing non-:class:`~hypothesis.HealthCheck` values in
>  :attr:`~hypothesis.settings.suppress_health_check`. This was previously
>  allowed but never did anything useful.

>In addition, passing a non-iterable value as :attr:`~hypothesis.settings.suppress_health_check`
>will now raise an error immediately (it would never have worked correctly, but
>it would previously have failed later). Some validation error messages have
>also been updated.

>This work was funded by `Smarkets &lt;https://smarkets.com/&gt;`_.

>-------------------


>### 3.36.1

>-------------------

>This is a yak shaving release, mostly concerned with our own tests.

>While :func:`~python:inspect.getfullargspec` was documented as deprecated
>in Python 3.5, it never actually emitted a warning.  Our code to silence
>this (nonexistent) warning has therefore been removed.

>We now run our tests with ``DeprecationWarning`` as an error, and made some
>minor changes to our own tests as a result.  This required similar upstream
>updates to :pypi:`coverage` and :pypi:`execnet` (a test-time dependency via
>:pypi:`pytest-xdist`).

>There is no user-visible change in Hypothesis itself, but we encourage you
>to consider enabling deprecations as errors in your own tests.

>-------------------


>### 3.36.0

>-------------------

>This release adds a setting to the public API, and does some internal cleanup:

>- The :attr:`~hypothesis.settings.derandomize` setting is now documented (:issue:`890`)
>- Removed - and disallowed - all &#39;bare excepts&#39; in Hypothesis (:issue:`953`)
>- Documented the :attr:`~hypothesis.settings.strict` setting as deprecated, and
>  updated the build so our docs always match deprecations in the code.

>-------------------


>### 3.35.0

>-------------------

>This minor release supports constraining :func:`~hypothesis.strategies.uuids`
>to generate :class:`~python:uuid.UUID`s of a particular version.
>(:issue:`721`)

>Thanks to Dion Misic for this feature.

>-------------------


>### 3.34.1

>-------------------

>This patch updates the documentation to suggest
>:func:`builds(callable) &lt;hypothesis.strategies.builds&gt;` instead of
>:func:`just(callable()) &lt;hypothesis.strategies.just&gt;`.

>-------------------


>### 3.34.0

>-------------------

>Hypothesis now emits deprecation warnings if you apply
>:func:`given &lt;hypothesis.given&gt;` more than once to a target.

>Applying :func:`given &lt;hypothesis.given&gt;` repeatedly wraps the target multiple
>times. Each wrapper will search the space of of possible parameters separately.
>This is equivalent but will be much more inefficient than doing it with a
>single call to :func:`given &lt;hypothesis.given&gt;`.

>For example, instead of
>``given(booleans()) given(integers())``, you could write
>``given(booleans(), integers())``

>-------------------


>### 3.33.1

>-------------------

>This is a bugfix release:

>- :func:`~hypothesis.strategies.builds` would try to infer a strategy for
>  required positional arguments of the target from type hints, even if they
>  had been given to :func:`~hypothesis.strategies.builds` as positional
>  arguments (:issue:`946`).  Now it only infers missing required arguments.
>- An internal introspection function wrongly reported ``self`` as a required
>  argument for bound methods, which might also have affected
>  :func:`~hypothesis.strategies.builds`.  Now it knows better.

>-------------------









That's it for now!

Happy merging! 🤖
bors-fusion bot added a commit to fusionapp/entropy that referenced this issue Nov 15, 2017
Merge #161
161: Scheduled weekly dependency update for week 46 r=mithrandi




## Updates
Here's a list of all the updates bundled in this pull request. I've added some links to make it easier for you to find all the information you need.
<table align="center">

<tr>
<td><b>attrs</b></td>
<td align="center">17.2.0</td>
<td align="center">&raquo;</td>
<td align="center">17.3.0</td>
<td>
     <a href="https://pypi.python.org/pypi/attrs">PyPI</a> | <a href="https://pyup.io/changelogs/attrs/">Changelog</a> | <a href="http://www.attrs.org/">Homepage</a> 

</td>

<tr>
<td><b>cryptography</b></td>
<td align="center">2.1.2</td>
<td align="center">&raquo;</td>
<td align="center">2.1.3</td>
<td>
     <a href="https://pypi.python.org/pypi/cryptography">PyPI</a> | <a href="https://pyup.io/changelogs/cryptography/">Changelog</a> | <a href="https://github.com/pyca/cryptography">Repo</a> 

</td>

<tr>
<td><b>lxml</b></td>
<td align="center">4.1.0</td>
<td align="center">&raquo;</td>
<td align="center">4.1.1</td>
<td>
     <a href="https://pypi.python.org/pypi/lxml">PyPI</a> | <a href="https://pyup.io/changelogs/lxml/">Changelog</a> | <a href="http://lxml.de/">Homepage</a> | <a href="https://bugs.launchpad.net/lxml">Bugtracker</a> 

</td>

<tr>
<td><b>pytz</b></td>
<td align="center">2017.2</td>
<td align="center">&raquo;</td>
<td align="center">2017.3</td>
<td>
     <a href="https://pypi.python.org/pypi/pytz">PyPI</a> | <a href="http://pythonhosted.org/pytz">Homepage</a> | <a href="http://pythonhosted.org/pytz/">Docs</a> 

</td>

</tr>
</table>



## Changelogs


### attrs 17.2.0 -> 17.3.0

>### 17.3.0

>-------------------

>Backward-incompatible Changes
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>- Attributes are not defined on the class body anymore.

>  This means that if you define a class ``C`` with an attribute ``x``, the class will *not* have an attribute ``x`` for introspection anymore.
>  Instead of ``C.x``, use ``attr.fields(C).x`` or look at ``C.__attrs_attrs__``.
>  The old behavior has been deprecated since version 16.1.
>  (`253 &lt;https://github.com/python-attrs/attrs/issues/253&gt;`_)


>Changes
>^^^^^^^

>- ``super()`` and ``__class__`` now work on Python 3 when ``slots=True``.
>  (`102 &lt;https://github.com/python-attrs/attrs/issues/102&gt;`_, `226 &lt;https://github.com/python-attrs/attrs/issues/226&gt;`_, `269 &lt;https://github.com/python-attrs/attrs/issues/269&gt;`_, `270 &lt;https://github.com/python-attrs/attrs/issues/270&gt;`_, `272 &lt;https://github.com/python-attrs/attrs/issues/272&gt;`_)
>- Added ``type`` argument to ``attr.ib()`` and corresponding ``type`` attribute to ``attr.Attribute``.

>  This change paves the way for automatic type checking and serialization (though as of this release ``attrs`` does not make use of it).
>  In Python 3.6 or higher, the value of ``attr.Attribute.type`` can alternately be set using variable type annotations
>  (see `PEP 526 &lt;https://www.python.org/dev/peps/pep-0526/&gt;`_). (`151 &lt;https://github.com/python-attrs/attrs/issues/151&gt;`_, `214 &lt;https://github.com/python-attrs/attrs/issues/214&gt;`_, `215 &lt;https://github.com/python-attrs/attrs/issues/215&gt;`_, `239 &lt;https://github.com/python-attrs/attrs/issues/239&gt;`_)
>- The combination of ``str=True`` and ``slots=True`` now works on Python 2.
>  (`198 &lt;https://github.com/python-attrs/attrs/issues/198&gt;`_)
>- ``attr.Factory`` is hashable again. (`204
>  &lt;https://github.com/python-attrs/attrs/issues/204&gt;`_)
>- Subclasses now can overwrite attribute definitions of their superclass.

>  That means that you can -- for example -- change the default value for an attribute by redefining it.
>  (`221 &lt;https://github.com/python-attrs/attrs/issues/221&gt;`_, `229 &lt;https://github.com/python-attrs/attrs/issues/229&gt;`_)
>- Added new option ``auto_attribs`` to ``attr.s`` that allows to collect annotated fields without setting them to ``attr.ib()``.

>  Setting a field to an ``attr.ib()`` is still possible to supply options like validators.
>  Setting it to any other value is treated like it was passed as ``attr.ib(default=value)`` -- passing an instance of ``attr.Factory`` also works as expected.
>  (`262 &lt;https://github.com/python-attrs/attrs/issues/262&gt;`_, `277 &lt;https://github.com/python-attrs/attrs/issues/277&gt;`_)
>- Instances of classes created using ``attr.make_class()`` can now be pickled.
>  (`282 &lt;https://github.com/python-attrs/attrs/issues/282&gt;`_)


>----








### lxml 4.1.0 -> 4.1.1

>### 4.1.1

>==================

>* Rebuild with Cython 0.27.3 to improve support for Py3.7.











That's it for now!

Happy merging! 🤖
bors-fusion bot added a commit to fusionapp/documint that referenced this issue Nov 17, 2017
Merge #118
118: Update attrs to 17.3.0 r=mithrandi


There's a new version of [attrs](https://pypi.python.org/pypi/attrs) available.
You are currently using **17.2.0**. I have updated it to **17.3.0**



These links might come in handy:  <a href="https://pypi.python.org/pypi/attrs">PyPI</a> | <a href="https://pyup.io/changelogs/attrs/">Changelog</a> | <a href="http://www.attrs.org/">Homepage</a> 



### Changelog
> 
>### 17.3.0

>-------------------

>Backward-incompatible Changes
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>- Attributes are not defined on the class body anymore.

>  This means that if you define a class ``C`` with an attribute ``x``, the class will *not* have an attribute ``x`` for introspection anymore.
>  Instead of ``C.x``, use ``attr.fields(C).x`` or look at ``C.__attrs_attrs__``.
>  The old behavior has been deprecated since version 16.1.
>  (`253 &lt;https://github.com/python-attrs/attrs/issues/253&gt;`_)


>Changes
>^^^^^^^

>- ``super()`` and ``__class__`` now work on Python 3 when ``slots=True``.
>  (`102 &lt;https://github.com/python-attrs/attrs/issues/102&gt;`_, `226 &lt;https://github.com/python-attrs/attrs/issues/226&gt;`_, `269 &lt;https://github.com/python-attrs/attrs/issues/269&gt;`_, `270 &lt;https://github.com/python-attrs/attrs/issues/270&gt;`_, `272 &lt;https://github.com/python-attrs/attrs/issues/272&gt;`_)
>- Added ``type`` argument to ``attr.ib()`` and corresponding ``type`` attribute to ``attr.Attribute``.

>  This change paves the way for automatic type checking and serialization (though as of this release ``attrs`` does not make use of it).
>  In Python 3.6 or higher, the value of ``attr.Attribute.type`` can alternately be set using variable type annotations
>  (see `PEP 526 &lt;https://www.python.org/dev/peps/pep-0526/&gt;`_). (`151 &lt;https://github.com/python-attrs/attrs/issues/151&gt;`_, `214 &lt;https://github.com/python-attrs/attrs/issues/214&gt;`_, `215 &lt;https://github.com/python-attrs/attrs/issues/215&gt;`_, `239 &lt;https://github.com/python-attrs/attrs/issues/239&gt;`_)
>- The combination of ``str=True`` and ``slots=True`` now works on Python 2.
>  (`198 &lt;https://github.com/python-attrs/attrs/issues/198&gt;`_)
>- ``attr.Factory`` is hashable again. (`204
>  &lt;https://github.com/python-attrs/attrs/issues/204&gt;`_)
>- Subclasses now can overwrite attribute definitions of their superclass.

>  That means that you can -- for example -- change the default value for an attribute by redefining it.
>  (`221 &lt;https://github.com/python-attrs/attrs/issues/221&gt;`_, `229 &lt;https://github.com/python-attrs/attrs/issues/229&gt;`_)
>- Added new option ``auto_attribs`` to ``attr.s`` that allows to collect annotated fields without setting them to ``attr.ib()``.

>  Setting a field to an ``attr.ib()`` is still possible to supply options like validators.
>  Setting it to any other value is treated like it was passed as ``attr.ib(default=value)`` -- passing an instance of ``attr.Factory`` also works as expected.
>  (`262 &lt;https://github.com/python-attrs/attrs/issues/262&gt;`_, `277 &lt;https://github.com/python-attrs/attrs/issues/277&gt;`_)
>- Instances of classes created using ``attr.make_class()`` can now be pickled.
>  (`282 &lt;https://github.com/python-attrs/attrs/issues/282&gt;`_)


>----








*Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.*

Happy merging! 🤖
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