Is there a Python shortcut for an __init__ that simply sets properties?

Question

It's sometimes common in Python to see __init__ code like this:

class SomeClass(object):
    def __init__(self, a, b, c, d, e, f, g):
        self.a = a
        self.b = b
        self.c = c
        self.d = d
        self.e = e
        self.f = f
        self.g = g

especially if the class in question is purely a data structure with no behaviour. Is there a (Python 2.7) shortcut for this or a way to make one?

Answer 1

You might find the attrs library helpful. Here's an example from the overview page of the docs:

>>> import attr
>>> @attr.s
... class SomeClass(object):
...     a_number = attr.ib(default=42)
...     list_of_numbers = attr.ib(factory=list)
...
...     def hard_math(self, another_number):
...         return self.a_number + sum(self.list_of_numbers) * another_number
>>> sc = SomeClass(1, [1, 2, 3])
>>> sc
SomeClass(a_number=1, list_of_numbers=[1, 2, 3])
>>> sc.hard_math(3)
19

If you were using Python 3.8+, you could use dataclasses.

>>> from typing import List
>>> from dataclasses import dataclass, field
>>> @dataclass
... class OtherClass:
...     a_number: int=42
...     list_of_numbers: List[int] = field(default_factory=list)
...     def hard_math(self, another_number):
...         return self.a_number + sum(self.list_of_numbers) * another_number
>>> OtherClass=SomeClass
>>> oc = OtherClass(1, [1, 2, 3])
>>> oc
SomeClass(a_number=1, list_of_numbers=[1, 2, 3])
>>> oc.hard_math(3)
19