nestio 0.2.0

Async-first nested storage with dot-path access and atomic writes — supports JSON, TOML, YAML, and TOON

nestio

Async-first nested storage with dot-path access and atomic writes.

nestio lets you read and write deeply nested data files using simple dot-path keys — no manual file handling, no race conditions, no boilerplate. Supports multiple file formats, with more on the way.

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Installation

pip install nestio

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Supported Formats

Format	Class	File ext	Best for
JSON	JSON	.json	General purpose, APIs, configs
TOML	TOML	.toml	Configuration files
YAML	YAML	.yaml	Human-friendly configs
TOON	TOON	.toon	LLM input — compact, token-efficient

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Quickstart

JSON

import asyncio
from nestio import JSON

async def main():
    db = JSON("data/config.json")

    await db.set("user.name", "Alice")
    await db.set("user.settings.theme", "dark")
    await db.set("user.scores", [])

    name = await db.get("user.name")            # "Alice"
    theme = await db.get("user.settings.theme") # "dark"

    await db.append("user.scores", 42)
    await db.update("user.settings", {"language": "en"})
    await db.delete("user.settings.theme")

asyncio.run(main())

TOML

import asyncio
from nestio import TOML

async def main():
    cfg = TOML("data/config.toml")

    await cfg.set("server.host", "localhost")
    await cfg.set("server.port", 8080)

    host = await cfg.get("server.host") # "localhost"

    await cfg.update("server", {"port": 9090, "debug": True})
    await cfg.delete("server.host")

asyncio.run(main())

YAML

import asyncio
from nestio import YAML

async def main():
    cfg = YAML("data/config.yaml")

    await cfg.set("server.host", "localhost")
    await cfg.set("server.port", 8080)
    await cfg.set("tags", ["web", "api"])

    host = await cfg.get("server.host") # "localhost"

    await cfg.append("tags", "async")
    await cfg.update("server", {"timeout": 30})
    await cfg.delete("server.port")

asyncio.run(main())

TOON

TOON (Token-Oriented Object Notation) is a compact, human-readable format designed for LLM input. It uses YAML-style indentation for nested objects and CSV-style rows for uniform arrays — achieving up to 40% fewer tokens than JSON while maintaining full round-trip fidelity.

import asyncio
from nestio import TOON

async def main():
    store = TOON("data/context.toon")

    await store.set("context.task", "Our favorite hikes")
    await store.set("context.location", "Boulder")
    await store.set("friends", ["ana", "luis", "sam"])

    task = await store.get("context.task") # "Our favorite hikes"

    await store.append("logs", "started")
    await store.update("context", {"season": "spring_2025"})
    await store.delete("context.location")

asyncio.run(main())

A .toon file produced by nestio looks like this:

context:
  task: Our favorite hikes
  season: spring_2025
friends[3]: ana,luis,sam
hikes[3]{id,name,distanceKm,wasSunny}:
  1,Blue Lake Trail,7.5,true
  2,Ridge Overlook,9.2,false
  3,Wildflower Loop,5.1,true

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API

All methods are async and must be awaited. JSON, TOML, YAML, and TOON all share the same interface.

JSON(path) / TOML(path) / YAML(path) / TOON(path)

Creates a storage instance pointing to a file. The file and any parent directories are created automatically on first write.

db    = JSON("path/to/file.json")
cfg   = TOML("path/to/file.toml")
cfg   = YAML("path/to/file.yaml")
store = TOON("path/to/file.toon")

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get(path, default=None)

Returns the value at the given dot-path, or default if it doesn't exist.

value = await db.get("server.host", default="localhost")

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set(path, value)

Sets the value at the given dot-path. Creates intermediate dicts as needed.

await db.set("server.port", 8080)

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delete(path)

Removes the key at the given dot-path. Does nothing if the key doesn't exist.

await db.delete("server.port")

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append(path, value)

Appends a value to a list at the given dot-path. Creates the list if it doesn't exist yet.

await db.append("logs", {"level": "info", "msg": "started"})

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update(path, new_data)

Deep-merges a dict into the value at the given dot-path. Nested keys are merged recursively — existing keys not in new_data are preserved.

await db.update("config", {"retries": 3, "timeout": 30})

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How it works

• Dot-path access — keys like "a.b.c" resolve through nested dicts automatically.
• Atomic writes — every save writes to a temp file first, then uses os.replace() to swap it in. Your file is never left in a half-written state.
• Per-key locking — concurrent writes to the same path are serialized with asyncio.Lock, while independent paths can write in parallel. Locks are cleaned up automatically after a TTL.

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Requirements

• Python 3.9+
• aiofiles
• pyyaml (for YAML support)
• tomli (Python < 3.11 only, for TOML support)
• tomli-w (for TOML support)
• toons (for TOON support)

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License

MIT © MrBaconHat