Backport python 3.7 dataclass

A new dataclass decorator was recently accepted into python 3.7 (https://www.python.org/dev/peps/pep-0557/).

The implementation seems similar to coconut’s implementation of the data type (subclassing the namedtuple) but they differ in terms of their syntax. I was just wondering whether coconut would keep the current syntax (for backward compatibility) or would it be changing to the new syntax (to avoid feature duplication). I just asked this question because I’m curious.

[Hong-Xiang]

For older versions of Python, we can get same functionality of dataclasses via attrs, as this says, it support PyPi, Python 2.7, 3.4+.

It supports

• frozen,
• __slot__,
• typed __eq__

import attr

@attr.s(auto_attribs=True)
class vector20:
    x: int
    y: int

@attr.s(auto_attribs=True)
class vector21:
    x: int
    y: int


print(vector20(0, 1) == vector20(0, 1)) # return True
print(vector20(0, 1) == vector21(0, 1)) # return False

and lots of other features.

I’m wondering if it is allowed to add this package as dependency of coconut?

If it is allowed, I’m wondering how to learn about the compiling process of data. I’ve found data_handle in L1202 of compiler/compiler.py, and it seems that for basic data support, only block after L1331 elif saw_defaults: should be modified, but there I’m confused of matching simple, docstring, e.t.c in stmts. How to learn this block of code? I can’t add break point to compiler, and adding print statement seems not work.

On the other hand, May data support annotations from [PEP 526]? Thus like

data vector2:
    x: int = 0
    y: int = 0

[benji-york]

The dataclass decorator accepts a “freeze” argument which makes the instances read-only (well, as read-only as anything gets in Python).

On Fri, Dec 8, 2017 at 3:27 PM, Dileep Kishore [e-mail] wrote:

@evhub https://github.com/evhub you’re right. I assumed they inherited from namedtuples but it looks like they just create normal classes.

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– Benji York