PyMeTTa

PyMeTTa is the Python extension. It is on PyPI as pymetta and imports as metta, and its tutorial installs it and runs a first program.

The extension is two directions at once, which is why its control file is the one that declares both entry/2 roles in two files:

title('MeTTa in Python: the janus bridge and the metta library''s transport').
needs(prolog_library(janus)).
entry(engine, 'bridge.pl').
entry(host, 'metta/shim.pl').

entry(engine, 'bridge.pl') is the ENGINE reaching Python: py-atom resolves a dotted name, py-call applies it, and a Python generator arrives as nondeterminism. The engine consults that file at boot. entry(host, 'metta/shim.pl') is Python reaching the ENGINE: it is the metta library's transport, consulted by the library when it boots, and the engine records it without ever loading it.

Its one need is library(janus), SWI's own Python bridge. A build without it, the WebAssembly build or a stripped install, cannot host this extension at all, so the extension loads nothing and says nothing rather than reporting a fault.

Its documentation is most of this site

This extension is the one you are reading about everywhere else:

• Tutorials teach MeTTa from Python, one concept at a time.
• Guide covers the surface by task: queries, definitions, spaces, threads, observability, notebooks.
• Integrations are the library boundaries: dataframes, DuckDB, Pydantic, arrays, HTTP.
• Live systems cover standing queries, remotes and the event loop.
• Reasoning covers custom matching and weighted relations.
• Reference reproduces every public module's signatures and docstrings, generated from the source.

Install SWI-Prolog first, then pip install 'pymetta[engine]', or pip install '.[engine]' from the repository root, or point METTA_PATH at a clone. The PyMeTTa tutorial walks that install and the first program; Install and first steps is the guide's version of the same ground.