autoinit

Python decorator for automatic initialization instance attributes

What

import autoinit  # same as `from autoinit import autoinit`

@autoinit
class X:
    def __init__(self, a, b, c, d:int, e=99.99, f='some_default_value'):
	    print("__init__ do some another things")

x = X(42, 100, 500, None)
#  Output: "__init__ do some another things"

print(x.__dict__)
# Output: {'a': 42, 'b': 100, 'c': 500, 'd': None, 'e': 99.99, 'f': 'some_default_value'}

How

$ pip install autoinit

Where

Tested in:

• CPython: 2.7, 3.5-3.11
• Pypy: 2.7, 3.5-3.9
• Jython: 2.7

...but with a high probability will work with other implementations as well.

Why

A lot of elementary assignments inside __init__ are a fairly frequent and rather dull case.

class FiveDimensionRecord:
    def __init__(self, x:int, y:int, z:int, u:int,
                 v:int, dt:typing.Optional[datetime]=None, description:str=''):
        self.x = x
        self.y = y
        self.z = z
        self.u = u
        self.v = v
        self.dt = dt or datetime.now()
        self.description = description

Dataclasses do not make it much more fun, mainly because you still cannot declare attributes in one line

@dataclass
class FiveDimensionRecord:
    x: int
    y: int
    z: int
    u: int
    v: int
    dt: 'typing.Any' = None
    description: str = ''

    def __post_init__(self):
        self.dt = self.dt or datetime.now()

With autoinit it looks much more compact and minimalistic

class FiveDimensionRecord:
    @autoinit
    def __init__(self, x:int, y:int, z:int,
                 u:int, v:int, dt=None, description:str=''):
        self.dt = self.dt or datetime.now()

Options

• @autoinit(exclude='attr') or @autoinit(exclude=['attr1', 'attr2]'): skip specified attributes. Default: []

• @autoinit(no_warn=True): do not throw warning if decorator applied to non-__init__ method. Default: False.

• @autoinit(reverse=True): invert the order of actions - first call the wrapped method (which is usually __init__), and then do assignment. Default: False.

The decorator itself can be equally applied to both the __init__ method and the entire class.