CapDAG for Python

This public package is the Python mirror of CapDAG. It provides Tagged, Media, and Cap URNs; capability definitions; registry resolution; Machine Notation; planning and execution; Bifaci; and the Python cartridge runtime and CLI.

Rust is the behavioral reference. Shared numbered tests carry the same meaning across mirrors, so current test catalogues—not a prose count—record parity.

Install the package

Python 3.11 or newer is required.

python3 -m pip install capdag

For a source checkout:

python3 -m pip install -e '.[dev]'

Parse and build Cap URNs

from capdag import CapUrn, CapUrnBuilder

parsed = CapUrn.from_string(
    'cap:disbind;in="media:document;ext=pdf";out="media:enc=utf-8;page"'
)
built = (
    CapUrnBuilder()
    .in_spec("media:document;ext=pdf")
    .out_spec("media:enc=utf-8;page")
    .marker("disbind")
    .build()
)

assert parsed.to_string() == built.to_string()

Treat URNs as opaque parsed values. Use their predicates for equivalence, conformance, dispatch, and ranking rather than splitting or comparing their serialized strings.

Find the relevant API

The package follows the boundaries in the CapDAG specification:

• capdag.urn contains Tagged, Media, and Cap URNs;
• capdag.cap contains definitions, argument sources, schema validation, and callers;
• capdag.machine and capdag.planner contain notation, planning, and execution structures;
• capdag.bifaci contains frames, streaming, flow control, cartridge and host runtimes, and relay components; and
• registry modules resolve versioned fabric and cartridge data.

Docstrings beside public Python objects are the language-specific API reference. Language-neutral rules belong to the canonical specification.

Scaffold a Python cartridge

capdag new sentiment-tagger --python
cd sentiment-tagger
capdag dev-install .
echo "I love this" | capdag sentiment-tagger

The generated project demonstrates a manifest, canonical URNs, handler registration, typed input and output, a model-backed peer call, and progress forwarding. See Build and Run a Cartridge.

Verify changes

python3 -m pytest

Run python3 -m pytest --cov=capdag when you also need a coverage report. Shared behavior changes require the applicable reference test with the same substantive number and assertions.

License

MIT