Installation

Probatio is pure Python. There is nothing to compile, no build step, and no native extension to match against your platform. Install it and import it.

Install

Pick your package manager:

uv

uv add probatio

pip

pip install probatio

Poetry

poetry add probatio

Supported Python versions

Probatio needs Python 3.12 or newer. It is tested on CPython 3.12, 3.13, 3.14, and 3.15. If you can run those, you can run Probatio.

Optional backends

The core has no runtime dependencies. What works on a bare install depends on the format, because the standard library does not ship a YAML parser or a TOML writer:

Format	Read	Write
JSON	standard library	standard library
TOML	standard library (tomllib)	needs the toml extra
YAML	needs the yaml or fast extra	needs the yaml or fast extra

When a faster backend is installed, Probatio reaches for it first. Three extras are available:

• fast: orjson for JSON and yamlrocks for YAML (speed, and YAML support).
• yaml: PyYAML, the portable YAML backend for environments without yamlrocks. Install this (or fast) if you load or dump YAML.
• toml: tomli-w for writing TOML. Reading TOML uses the standard library’s tomllib, so reading needs no extra.

Without a YAML backend, load_yaml/dump_yaml raise a clear RuntimeError telling you which extra to install; the same goes for dump_toml without the toml extra. JSON and TOML reading always work.

Install one or more extras:

uv

uv add "probatio[fast]"
uv add "probatio[yaml,toml]"

pip

pip install "probatio[fast]"
pip install "probatio[yaml,toml]"

Poetry

poetry add "probatio[fast]"
poetry add "probatio[yaml,toml]"

Note

The extras are about speed and YAML writing, not features. A schema validates the same way with or without them.

Confirm it works

A tiny schema, validated:

from probatio import Schema, Required, Optional

schema = Schema(
    {
        Required("name"): str,
        Optional("port", default=8080): int,
    }
)

schema({"name": "app"})  # {'name': 'app', 'port': 8080}

If that returns the dict with port filled in, you are set. Read the quick start next.