Adding __slots__ to a class in Python is a great way to improve performance.
But to work properly, all base classes need to implement it — without overlap!
It's easy to get wrong, and what's worse: there is nothing warning you that you messed up.
✨ Until now! ✨
slotscheck helps you validate your slots are working properly.
You can even use it to enforce the use of slots across (parts of) your codebase.
See my blog post
for the origin story behind slotscheck.
Usage is quick from the command line:
python -m slotscheck [FILES]...
# or
slotscheck -m [MODULES]...For example:
$ slotscheck -m sanic
ERROR: 'sanic.app:Sanic' defines overlapping slots.
ERROR: 'sanic.response:HTTPResponse' has slots but superclass does not.
Oh no, found some problems!
Scanned 72 module(s), 111 class(es).Now get to fixing —
and add slotscheck to your CI pipeline or
pre-commit
to prevent mistakes from creeping in again!
See here and
here for examples.
- Detect broken slots inheritance
- Detect overlapping slots
- Detect duplicate slots
- Pre-commit hook
- (Optionally) enforce the use of slots
See the documentation for more details and configuration options.
Flake8 plugins need to work without running the code. Many libraries use conditional imports, star imports, re-exports, and define slots with decorators or metaclasses. This all but requires running the code to determine the slots and class tree.
There's an issue to discuss the matter.
slotscheckwill try to import all submodules of the given package. If there are scripts withoutif __name__ == "__main__":blocks, they may be executed.- Even in the case that slots are not inherited properly,
there may still be an advantage to using them
(i.e. attribute access speed and some memory savings).
However, in most cases this is unintentional.
slotscheckallows you to ignore specific cases. - Because
slotscheckimports your code in arbitrary order, it can—in rare cases—result in confusing and randomly-occurring import errors in third-party libraries. In such a case, it is recommended to omit modules such as your tests and mypy plugins from the slotscheck run. See here. Alternatively, you can usePYTHONHASHSEED=<any value>to make the import order deterministic. A solution to this problem is being worked on in this issue.
It's available on PyPI.
pip install slotscheck