autoslot 2017.10.3

autoslot

autoslot

Automatic “__slots__”.

Demo

from autoslot import Slots

class Compact(Slots):
    def __init__(self, a, b):
        self.x = a
        self.y = b

This produces _exactly_ the same class as if you had done:

class Compact:
    __slots__ = {'x', 'y'}
    def __init__(self, a, b):
        self.x = a
        self.y = b

The benefit of using the metaclass version is that you can modify the code inside the __init__() method to add more attributes, and those changes will automatically be reflected in the __slots__ definition.

How does it work?

See for yourself–the code is embarrassingly small!

In words: the metaclass finds the __init__() method, if present, and accesses its bytecode. It looks for all assignments to attributes of self, and considers those to be desired __slots__ entries. Then the metaclass injects __slots__ into the namespace of the class definition and thereafter allows class creation to proceed as normal.

Note

If __init__ is missing, the class will not have __slots__ injected. It will be a normal class with a __dict__ attribute.