Contents

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 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={"m", "f", "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:

3.13
3.12
3.11

Note

I’m only one person, so to keep from getting overwhelmed, I’m only committing to supporting the 3 most recent versions of Python.

Installation

Install the latest stable version via pip:

pip install phx-filters

Important

Make sure to install phx-filters, not filters. I created the latter at a previous job years ago, and after I left they never touched that project again and stopped responding to my emails — so in the end I had to fork it 🤷

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]
```

Tip

To install multiple extensions, separate them with commas, e.g.:

pip install phx-filters[django,iso]

Happy filtering!