slotscheck 0.1.1

Check the usage of __slots__.

Adding __slots__ to a class in Python is a great way to reduce memory usage. But to work properly, all base classes need to implement it. It turns out it’s easy to forget one class in complex inheritance trees. What’s worse: there is nothing warning you that you messed up.

✨ Until now! ✨

Quickstart

Usage is quick from the command line:

slotscheck [MODULE]

For example:

$ slotscheck pandas
ERROR: 'pandas.core.internals.array_manager.SingleArrayManager' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.blocks.Block' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.blocks.NumericBlock' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.blocks.DatetimeLikeBlock' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.blocks.ObjectBlock' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.blocks.CategoricalBlock' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.array_manager.BaseArrayManager' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.managers.BaseBlockManager' has slots but inherits from non-slot class
ERROR: 'pandas.core.internals.managers.SingleBlockManager' has slots but inherits from non-slot class

Now get to fixing – and add slotscheck to your CI pipeline to prevent mistakes from creeping in again!

Use the --help option to find out more.

Notes

• slotscheck will try to import all submodules of the given package. If there are scripts without if __name__ == "__main__": blocks, they may be executed.

• Even in the case that slots are not inherited properly, there may still an advantage to using them (i.e. attribute access speed and some memory savings)

• Only classes at module-level are checked (i.e. no nested classes)

• In rare cases imports may fail, the module is then skipped. Use the verbose mode to show detailed information.

• Limited to the CPython implementation for now.

• Non pure-Python classes are currently assumed to have slots. This is not necessarily the case, but it is nontrivial to determine.

Installation

It’s available on PyPI.

pip install slotscheck