guatiao for Python

Python bindings for the guatiao ABI: one value model for passing data between languages, a JSON Schema that describes a value, and a registry that loads plugin libraries. Pure Python over ctypes, with no dependencies and nothing to compile. It works with any shared library that exports the ABI, whether that is guatiao itself or an application that carries it.

Status: alpha. A pure Python package: it carries no native library, you point it at one.

Features

• Value trees as Python objects — build, read and change a tree in place, or convert it to and from plain dict/list data.
• Numbers keep their exact text — 1.10 stays 1.10 and an integer of any size survives; you choose int/float, Decimal or str when reading.
• Be a plugin host — scan a directory, filter on what a library declares before loading it, list providers best first, build an instance from a configuration, call a provider through its table.
• JSON, TOML and YAML, and form checks against a schema, through the guatiao-serde and guatiao-intake libraries when they are present.
• Importing never fails — a native library is looked for on first use, and a missing one says every place that was searched.

Installation

pip install guatiao

The package drives a shared library that exports the guatiao ABI. Say where it is:

export GUATIAO_LIBRARY=/opt/myapp/lib             # a directory holding guatiao.dll / libguatiao.so / libguatiao.dylib
export GUATIAO_LIBRARY=/opt/myapp/myapp.dll       # or the file itself, whatever it is called

Without the variable the package tries the system's library search (ctypes.util.find_library("guatiao")). Nothing is loaded at import time: import guatiao always succeeds, and the first native call raises guatiao.LibraryNotFound, naming every place it looked. A library that exports only part of the ABI is fine: calling a function it lacks raises guatiao.MissingSymbol naming it, and everything else works.

guatiao_serde and guatiao_intake are looked for the same way, in the same directory, only when guatiao.serde or guatiao.intake is first used.

Quick start

Values

from guatiao import Value

with Value(host="10.0.0.1", port=5900, tags=["a", "b"]) as v:
    m = v.as_map()
    m["port"] = 5901
    m["tags"].as_list().append("c")

    m["port"].to_python()        # 5901
    list(m)                      # ['host', 'port', 'tags'], insertion order
    "missing" in m               # False; m["missing"] raises KeyError
    m["port"].int_or(22)         # 5901, or 22 if it were not an integer
    v.to_python()                # back to a plain dict

A Value owns its tree and frees it on close() or at the end of the with block. m["tags"] is a Ref: a path into the tree that is walked again on every access, so it stays valid while the tree grows around it.

Numbers keep their exact text. 1.10 stays 1.10, and an integer of any size survives. Choose what comes back when reading:

v = Value.number("1.10")
v.to_python()                    # 1.1   ("auto": int when it looks like one, else float)
v.to_python(numbers="decimal")   # Decimal('1.10')
v.to_python(numbers="str")       # '1.10'

Value(1), Value(True), Value("x"), Value([1, 2]) and Value({"host": "h"}, port=1) all work, as the builtins would. None becomes null, bytes the bytes kind, a dict with str keys a map. A missing value reads back as guatiao.ABSENT, which is falsy and is not None. A float that is nan or infinite raises ValueError.

Hosting plugins

from guatiao import Registry

with Registry("my-host", "1.0") as reg:
    report = reg.scan_dir("/opt/myapp/plugins", rules="kind=greeter")
    for p in reg.providers("greeter"):           # best first
        print(p["key"], p["version"], p["from"])

    reg.why_not("codec")                         # why nothing serves a kind

    schema = reg.provider_config("acme_shouter")   # borrowed; do not close
    with reg.create("acme_shouter", {"prefix": "hey"}) as instance:
        ...

    reg.retire("acme")                           # out of the registry, still mapped
    reg.unload("acme")                           # and unmapped, on your word

Every answer that is data comes back as a plain dict or list. rules is one [!]KEY=VALUE per line and filters on what a library declares about itself, before it is loaded.

To call a provider, describe its table with the ctypes.Structure the kind's C header declares and let the package check it:

from guatiao import kinds

table_ptr, size, ctx = reg.provider_table("acme_greeter", kind="greeter")
greeter = kinds.table(table_ptr, size, GreeterVtable, floor_hash=FLOOR_HASH)
greeter.greet(ctx, name, out_map, err)

tests/test_greeter.py is a complete worked example.

JSON, TOML, YAML and forms

from guatiao import serde, form

value = serde.loads('{"port": 5900}')                  # format="json" by default
text = serde.dumps(value, format="yaml")
pretty = serde.dumps(value, pretty=True)

problem = form.check(schema, form_doc)                 # None when the form fits the schema
sections = form.layout(schema, form_doc)
shown = form.is_visible(schema, form_doc, "tls.verify", values)

A format the loaded library does not export raises NotImplementedError naming it.

Errors

A failed native call raises guatiao.GuatiaoError, as one of BadValue, AllocFailed, WrongKind, NotFound, NullArgument, Gone, Unsupported, Busy or Internal. .status is the C status code, and .message carries a provider's own words when it gave any.

Known limits

• Reading JSON writes an exponent's sign: 1e400 parses as 1e+400. Everything else about a number's text survives a round trip.
• List.insert and list[i] = x rebuild the list, because the C ABI only appends and removes. append and del list[i] are direct.
• A Registry is used from one thread at a time, and a Value is not shared between threads without a lock of your own.
• Registry.unload unmaps a library, and nothing can check that you have released what you took from it first -- every value it built through its own allocator, every table, ctx and Instance. retire has no such condition and leaves the library mapped.

API overview

AGENTS.md is the full API reference and ships inside the wheel. The C ABI is described by guatiao.h.

Development

pip install -e "bindings/python[dev]"     # from the repository root, in a virtual environment
pytest bindings/python/tests -rs

The tests need the three libraries and the repository's example plugins in one directory. conftest.py points GUATIAO_LIBRARY at the repository's build output when the variable is unset; the repository's own AGENTS.md says how to produce it. With everything present nothing skips; a test that needs a missing library skips and says which. CI runs the suite on Python 3.9 and 3.14.

License

MPL 2.0 — see LICENSE.