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Attrs – the Python library everyone needs (2016)

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Re: Attrs – the Python library everyone needs (2016)

#51

Post by nauticacom »

atorodius wrote: post #46
nauticacom wrote: post #42

I've never understood the appeal of these "define struct-like-object" libraries (in any language; I've never understood using the standard library's "Struct" in Ruby). My preferred solution for addressing complexity is also to decompose the codebase into small, understandable, single-purpose objects, but so few of them end up being simple value objects like Point3D. Total ordering and value equality make sense for va…

well one appeal is that you dont have to write constructors, that‘s already enough of a win for me. then you get sane eq, and sane str, and already you remove 90% boilerplate

I really, genuinely don't get the appeal. I don't follow the "less code = better" ideology so maybe that's a contributor but I really don't see how this:

    class Person:
        def __init__(self, name, age):
            self.name = name
            self.age = age
is any worse than this:

    @dataclass
    class Person:
        name: str
        age: int
I'm not writing an eq method or a repr method in most cases, so it just doesn't add much for the cost.

Re: Attrs – the Python library everyone needs (2016)

#52

Post by skrtskrt »

ledauphin wrote: post #38
ahurmazda wrote: post #26

Earlier quoted context omitted.

Thanks. You do make a lot of good points. Attrs just has the features I need for now. It certainly feel a touch verbose but I’m happy to pay the price.

can you tell me which parts feel verbose? In my recent usage, I've not found myself using the older, more verbose approaches.

If you use the runtime type validators along with the python builtin type hints you constantly repeat yourself:

    id: UUID = attr.ib(validator=instance_of(UUID), …other parameters)
The type hint helps mypy and pylint work, while the validator is a runtime check by Attrs

If your attribute name is longer or you have other parameters to set, that can be a very long line (or lines) of code that you repeat for every attribute

Re: Attrs – the Python library everyone needs (2016)

#53

Post by pletnes »

rguillebert wrote: post #19
nsonha wrote: post #7

Earlier quoted context omitted.

Not a python guy, so confused as to why a thing called namedtuple behaves like dataclasses, what are their different usecases?

Namedtuples also behave like tuples, which is great when you want to incrementally turn tuples into classes but if you want an easy way of creating classes, it's probably not a good idea to have them behave like tuples. Plus dataclasses have more features.

There’s also the fact that sometimes you need an actual tuple - in some places (C extensions like numpy, opencv, …) and a dataclass just doesn’t work.

Re: Attrs – the Python library everyone needs (2016)

#54

Post by michaelcampbell »

nauticacom wrote: post #51
atorodius wrote: post #46

Earlier quoted context omitted.

well one appeal is that you dont have to write constructors, that‘s already enough of a win for me. then you get sane eq, and sane str, and already you remove 90% boilerplate

I really, genuinely don't get the appeal. I don't follow the "less code = better" ideology so maybe that's a contributor but I really don't see how this: class Person: def __init__(self, name, age): self.name = name self.age = age is any worse than this: @dataclass class Person: name: str age: int I'm not writing an eq method or a repr method in most cases, so it just doesn't add much for the cost.

Given that code is for people, I've never found a certain amount of idiomatic boilerplate a problem. The desire to remove it all, or magicify it away (eg: Django) has always made me do a bit of an internal eye roll.

Re: Attrs – the Python library everyone needs (2016)

#55

Post by geofft »

avidphantasm wrote: post #29
falafelite wrote: post #5

Earlier quoted context omitted.

Came here to say this, dataclasses have been super helpful for a big part of the pain point highlighted by the author. More often than not, that is enough for me.

Yes. There needs to be a very good reason for me to pull in a third party library (in this day and age, given supply chain attacks, etc.). I don’t see what Attrs gives me that dataclasses does not.

Huh, it's the other way around for me. Just about every nontrivial Python project I write requires at least one third-party library, and one much more complicated than attrs at that, that I may as well use attrs too. All the complexity of having dependencies - both distributing them / setting up a virtualenv / etc., and whatever scrutiny I wish to do on dependencies - have a pretty big constant term from doing them at all; doing them for one more dependency (and one that doesn't change all that often) is only a bit more work.

Granted, I'm not reviewing my third-party dependencies line by line when I upgrade them. But also I'm more afraid of the security risks of large amounts of in-house code that aren't exposed to public scrutiny, and so a policy that dissuaded the use of even high-quality and well-regarded third-party dependencies seems like it would do more harm than good.

Besides that, it helps that I happen to have met the maintainer of attrs at PyCon (and attrs has only one uploader in PyPI), and therefore I'm less concerned about supply-chain attacks against it, whether of the malicious-maintainer variety or the maintaner-got-scammed-or-hacked variety, than, again, most of my other dependencies whose maintainers I've never heard of. I'm not sure this scales particularly well, but I do feel like there's still something in the open source community being a community.

Re: Attrs – the Python library everyone needs (2016)

#56

Post by dang »

Past related threads:

Attrs – The python library everyone needs (2016) - https://news.ycombinator.com/item?id=17160262 - May 2018 (2 comments)

Using attrs for everything in Python - https://news.ycombinator.com/item?id=12359522 - Aug 2016 (101 comments)

The One Python Library Everyone Needs - https://news.ycombinator.com/item?id=12285342 - Aug 2016 (1 comment)

Re: Attrs – the Python library everyone needs (2016)

#57

Post by tddispointless »

I used attrs in a large python project, and it was more pain than it was worth. Off the top of my head, knowing the difference between factory vs default in the initializer was a bug that bit us, inheritance was painful because we were forced to redefine the attrs from the parent class in each child class (maybe they fixed this now). Validators were broken somehow. I even made a GitHub issue for this which was never addressed. Attrs are good for simple stuff. I feel plain old classes are more reliable once things get complex. And for simple things, dataclasses do just fine too.

Re: Attrs – the Python library everyone needs (2016)

#59

Post by Spivak »

nauticacom wrote: post #51
atorodius wrote: post #46

Earlier quoted context omitted.

well one appeal is that you dont have to write constructors, that‘s already enough of a win for me. then you get sane eq, and sane str, and already you remove 90% boilerplate

I really, genuinely don't get the appeal. I don't follow the "less code = better" ideology so maybe that's a contributor but I really don't see how this: class Person: def __init__(self, name, age): self.name = name self.age = age is any worse than this: @dataclass class Person: name: str age: int I'm not writing an eq method or a repr method in most cases, so it just doesn't add much for the cost.

The advantage of dataclasses is that they’re hard to mess up. They define all the methods you need to have an ergonomic idiomatic class that is essentially a tuple with some methods attached and have enough knobs to encompass basically all “normal” uses of classes.

It’s a pretty good abstraction that doesn’t feel half as magic as it is.

Re: Attrs – the Python library everyone needs (2016)

#60

Post by bjourne »

atorodius wrote: post #49

This is only remotely relevant but I recently learned that the related `dataclasses` is implemented by constructing _string representations_ of functions and calling `exec` on them. https://github.com/python/cpython/blob/3.10/Lib/dataclasses.... Kind of blew my mind

Ew. How can there not be some better way to do it?
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