New submission from Arie Bovenberg :
As discussed in bpo-46382, dataclasses may want to support the __weakref__ slot.
Currently, automatically slotted dataclasses are not given a __weakref__ slot.
This makes auto-slotted dataclasses incompatible with weakref.
The attrs library has chosen
Change by Arie Bovenberg :
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keywords: +patch
pull_requests: +30070
stage: -> patch review
pull_request: https://github.com/python/cpython/pull/31980
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Arie Bovenberg added the comment:
@eric.smith awesome!
What would you like to do about the __weakref__ slot?
1. take no action
2. create a separate ticket to discuss further
3. implement as done in attrs, now that we're changing __slots__ dataclass
behavior anyway
I wouldn't recommend (1
Arie Bovenberg added the comment:
@eric.smith did you give this some thought? Would we want to imitate the attrs
behavior regarding __weafref__?
It'd be nice if I can submit a PR to be included in 3.11
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<ht
Arie Bovenberg added the comment:
Thanks @gregory.p.smith! I didn't know about discuss.python.org. I created a
new topic there:
https://discuss.python.org/t/safer-logging-methods-for-f-strings-and-new-style-formatting/13802
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Arie Bovenberg added the comment:
@rhettinger @tinchester I definitely see now that f-strings should have a place
in logging.
But do you agree that f-strings don't mix 100% safely with the current logger
API?
What are your thoughts on a safer set of logger functions (see my comments
above
Arie Bovenberg added the comment:
@hynek interesting!
The discussion in https://github.com/python-attrs/attrs/pull/420 on the weakref
slot is very interesting as well.
Considering __weakref__ is something we don't want to make impossible in
dataclasses, @eric.smith what would be your
Arie Bovenberg added the comment:
Spencer is correct.
The documentation even adds: "This renders the meaning of the program
undefined."
It's clear it doesn't break anything users would often encounter (we would have
heard about it), but it's still undefine
Arie Bovenberg added the comment:
There are already 2 complexities I can think of:
1. This behavior may break some people's code, if they use __slots__ to iterate
over
the fields of a dataclass. Solution: explicitly mention in the docs that
not every field may get a slot on the new
New submission from Arie Bovenberg :
@dataclass(slots=True) adds slots to dataclasses. It adds a slot per field.
However, it doesn't account for slots already present in base classes:
>>> class Base:
... __slots__ = ('a', )
...
>>> @dataclass(slots=True)
New submission from Arie Bovenberg :
Recently, I've identified some __slots__-related mistakes in the stdlib
(bpo-46247, bpo-46244, bpo-46246).
Looking forward, it'd be wise to automate this check so mistakes don't creep
into the code in the future.
Implementation-wise, the most
Change by Arie Bovenberg :
--
keywords: +patch
pull_requests: +28656
stage: -> patch review
pull_request: https://github.com/python/cpython/pull/30452
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Change by Arie Bovenberg :
--
keywords: +patch
pull_requests: +28650
stage: -> patch review
pull_request: https://github.com/python/cpython/pull/30444
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Python tracker
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Arie Bovenberg added the comment:
@kj I would very much like to! Seems like a good place to start contributing :)
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Python tracker
<https://bugs.python.org/issue46
Arie Bovenberg added the comment:
@jaraco thanks for your quick response.
In short: __slots__ allows class layout to be optimized by replacing the class
__dict__ with specific descriptors. This results in a class where only specific
attributes can be get/set.
However, you only really get
New submission from Arie Bovenberg :
(as instructed in bpo-46244, I've created this ticket)
The classes Node and DocumentLS don't define __slots__, but a number of
subclasses do.
This appears to be a mistake.
If so, I'd like to create a PR to fix it.
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components: Library (Lib
New submission from Arie Bovenberg :
(as instructed in bpo-46244, I've created this ticket)
The subclass `EntryPoints` defines __slots__, but its base `DeprecatedList`
does not.
This appears to be a mistake.
If so, I'd like to create a PR to fix it.
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components: Library (Lib
Arie Bovenberg added the comment:
Thanks! I'll open new issues shortly on xml and importlib
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Python tracker
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Arie Bovenberg added the comment:
I've also encountered other classes in the stdlib possibly missing slots:
- importlib.metadata.DeprecatedList (subclass EntryPoints has slots)
- xml.dom.minidom.Node, xml.dom.xmlbuilder.DocumentLS (5 subclasses have slots)
Will investigate
New submission from Arie Bovenberg :
The mixin class "typing._TypeVarLike" has no __slots__. Its subclasses do
define __slots__, so it looks like a mistake.
Agree?
It should be an easy fix, and I'd like to pick this up.
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components: Library (Lib)
messages: 4
Arie Bovenberg added the comment:
Indeed the `__format__` style offers a lot more options (see
https://pyformat.info/).
Regarding performance you make an interesting point.
One possible solution is to allow f-strings _only_ if there are no args/kwargs.
In that one case formatting would
Arie Bovenberg added the comment:
I've done some more digging, and have read the related issue bpo-30995.
There are IMHO two challenges that are worth tackling:
1. A great number[1] of developers do their own string formatting.
This is sub-optimal for performance and - in rare cases
Arie Bovenberg added the comment:
Absolutely agree! In practice I find some people are not swayed by this
argument -- and prefer the readability of f-strings.
My expectation is that a clear recommendation in the official docs will
convince more people. Especially if there are security
New submission from Arie Bovenberg :
(I've already submitted this issue to secur...@python.org, who directed me to
propose a documentation change here)
Logging f-strings is quite popular, because the `%` style of logging is often
considered ugly.
However, logging preformatted strings comes
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