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Pre-commit hooks

Another alternative is to try to catch code quality issues before any code is even sent to the remote git repo. Pre-commit hooks are essentially actions that are taken right before code is committed to your (local) repo.

Pre-commit illustrated

Pre-commit package

There are different ways to create new hooks to your git repo. pre-commit is a package to easily config pre-commit hooks, and store them in a very readable manner.


To install, simply run:

pip install pre-commit



databooks meta

To use pre-commit with databooks meta, create a .pre-commit-config.yaml in the root of your project. There, include

-   repo:
    rev: 1.0.1
    -   id: databooks-meta

databooks repo has minimal configuration (such as the meta command). The rev parameter indicates the version to use and args indicate additional arguments to pass to the tool.

The pre-commit tool doesn't actually commit any changes if the staged files are modified. Therefore, if there is any unwanted metadata at the time of committing the changes, the files would be modified, no commit would be made, and it'd be up to the developer to inspect the changes, add them and commit. That's why we specify args: ["--overwrite"] by default.

databooks assert

To use databooks assert you must pass similar values, added with an args field to write your checks. Those can be a recipe or an expression, similarly to what would be done via the CLI. The difference here is that we pass an "extra check" that evaluates to True (namely databooks assert --expr "True") to allow a user to commit in case there are no tests in the configuration file.

-   repo:
    rev: 1.0.1
    -   id: databooks-assert
        args: ['--expr', 'len(nb.cells) < 10', '--recipe', 'seq-exec']


Once the configuration is in place all the user needs to do to trigger pre-commit is to commit changes normally

$ git add path/to/notebook.ipynb
$ git commit -m 'a clear message'
- hook id: databooks-assert
- exit code: 1

[12:24:10] INFO     path/to/notebook.ipynb failed 0 of 3 checks.
  Running assert checks ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00
           INFO     Found issues in notebook metadata for 1 out of 1

- hook id: databooks-meta
- files were modified by this hook

[23:24:11] WARNING  1 files will be overwritten             
  Removing metadata ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00
           INFO     The metadata of 1 out of 1 notebooks were

Alternatively, one could run pre-commit run to manually run the same command that is triggered right before committing changes. Or, one could run pre-commit run --all-files to run the pre-commit hooks in all files (regardless if the files have been staged or not). The latter is useful as a first-run to ensure consistency across the git repo or in CI.