Filters

The Filters library provides an easy and readable way to create complex data validation and processing pipelines, including:

• Validating complex JSON structures in API requests or config files.
• Parsing timestamps and converting to UTC.
• Converting Unicode strings to NFC, normalizing line endings and removing unprintable characters.
• Decoding Base64, including URL-safe variants.

And much more!

The output from one filter can be piped into the input of another, enabling you to chain filters together to quickly and easily create complex data schemas and pipelines.

Examples

Validate a latitude position and round to manageable precision:

(
    f.Required |
    f.Decimal |
    f.Min(Decimal(-90)) |
    f.Max(Decimal(90)) |
    f.Round(to_nearest='0.000001')
).apply('-12.0431842')

Parse an incoming value as a datetime, convert to UTC and strip tzinfo:

f.Datetime(naive=True).apply('2015-04-08T15:11:22-05:00')

Convert every value in an iterable (e.g., list) to unicode and strip leading/trailing whitespace. This also applies Unicode normalization, strips unprintable characters and normalizes line endings automatically.

f.FilterRepeater(f.Unicode | f.Strip).apply([
    b'\xe2\x99\xaa ',
    b'\xe2\x94\x8f(\xc2\xb0.\xc2\xb0)\xe2\x94\x9b ',
    b'\xe2\x94\x97(\xc2\xb0.\xc2\xb0)\xe2\x94\x93 ',
    b'\xe2\x99\xaa ',
])

Parse a JSON string and check that it has correct structure:

(
    f.JsonDecode |
    f.FilterMapper(
        {
            'birthday':  f.Date,
            'gender':    f.CaseFold | f.Choice(choices={'f', 'm', 'n'}),

            'utcOffset':
                f.Decimal |
                f.Min(Decimal('-15')) |
                f.Max(Decimal('+15')) |
                f.Round(to_nearest='0.25'),
        },

        allow_extra_keys   = False,
        allow_missing_keys = False,
    )
).apply('{"birthday":"1879-03-14", "gender":"M", "utcOffset":"1"}')

Requirements

Filters is known to be compatible with the following Python versions:

• 3.12
• 3.11
• 3.10

Installation

Install the latest stable version via pip:

pip install phx-filters

Extensions

The following extensions are available:

• Django Filters: Adds filters designed to work with Django applications. To install:

  pip install phx-filters[django]
  

• ISO Filters: Adds filters for interpreting standard codes and identifiers. To install:

  pip install phx-filters[iso]
  

pip install phx-filters[django,iso]

Running Unit Tests

Install the package with the test-runner extra to set up the necessary dependencies, and then you can run the tests with the tox command:

pip install -e .[test-runner]
tox -p

To run tests in the current virtualenv:

python -m unittest

Documentation

Documentation is available on ReadTheDocs.

If you are installing from source (see above), you can also build the documentation locally:

1. Install extra dependencies (you only have to do this once):

   pip install '.[docs-builder]'
   

2. Switch to the docs directory:

   cd docs
   

3. Build the documentation:

   make html
   

Releases

Steps to build releases are based on Packaging Python Projects Tutorial

1. Build the Project

1. Install extra dependencies (you only have to do this once):

   pip install -e '.[build-system]'
   

2. Delete artefacts from previous builds, if applicable:

   rm dist/*
   

3. Run the build:

   python -m build
   

4. The build artefacts will be located in the dist directory at the top level of the project.

2. Upload to PyPI

1. Create a PyPI API token (you only have to do this once).

2. Increment the version number in pyproject.toml.

3. Check that the build artefacts are valid, and fix any errors that it finds:

   python -m twine check dist/*
   

4. Upload build artefacts to PyPI:

   python -m twine upload dist/*
   

3. Create GitHub Release

1. Create a tag and push to GitHub:

   git tag <version>
   git push
   

   <version> must match the updated version number in pyproject.toml.

2. Go to the Releases page for the repo.

3. Click Draft a new release.

4. Select the tag that you created in step 1.

5. Specify the title of the release (e.g., Filters v1.2.3).

6. Write a description for the release. Make sure to include: - Credit for code contributed by community members. - Significant functionality that was added/changed/removed. - Any backwards-incompatible changes and/or migration instructions. - SHA256 hashes of the build artefacts.

7. GPG-sign the description for the release (ASCII-armoured).

8. Attach the build artefacts to the release.

9. Click Publish release.