attrs: Classes Without Boilerplate

27

attrs: Classes Without Boilerplate ☶ python attrs.org
via hawski 10 months ago | cached | 8 comments

8

A short and dumb example:

import attr

@attr.s
class Vec2(object):
        x = attr.ib()
        y = attr.ib()

pos = Vec2(42, -42)

11

hwayne edited 10 months ago | link

attrs has been successful enough that ~~PSF~~ CPython core is investigating adding a stripped-down version to the 3.7 standard library.
1. 8
  
  alex_gaynor 10 months ago | link
  
  It’s not the PSF, it’s the CPython core developers. The PSF does not direct the development of the Python language.
6

clacke 10 months ago | link

This looks really nice. Simple, does what it does, gets out of the way.

Sounded unnecessary, but http://www.attrs.org/en/stable/why.html explains the rationale well, in contrast with named tuples and other things.
3
alva edited 10 months ago | link
This gets close to a thing I enjoy in Swift:
```
struct Vec2 {
    var x: Float
    var y: Float
}

var pos = Vec2(x: 42, y: -42)
```
Free memberwise initializer for structs. You can also provide default values by appending = val to the members. The @dataclass proposal looks closer still.

You don’t get free comparison operators (but it’s getting there) so this is nicer in that regard.
1. 3
  
  andyc edited 10 months ago | link
  
  Yup I think this is basically “value types” for Python! I wanted this a long time ago!
  
  Namedtuple was close but the syntax is a bit awkward.
2. 3
  hawski edited 10 months ago | link
  In C99 you can do this:
  
  typedef struct { float x; float y; } Vec2; Vec2 pos_foo = {42, -42}; // or using designated initializers (x will be 0 in this case): Vec2 pos_bar = {.y = 42 }; // or using compound literals: draw(foo, (Vec2){42, -42}); // more with designated initializers (everything else will be 0): enum { FOO, BAR, BAZ, COUNT }; Vec2 pos[COUNT] = { [BAR] = {.y = 42} };
3. 2
  
  ngrilly 10 months ago | link
  
  It’s funny that statically typed languages like Swift and Go cover this better than a dynamically typed language like Python ;-)
  1. 1
    
    untitaker 10 months ago | link
    
    Not sure what this has to do with dynamic vs static typing.