PyTOON

PyTOON is a Python port of the excellent toon project by Johann Schopplich. It converts arbitrary Python data structures into the same concise, human-readable text representation produced by the original TypeScript encoder.

The goal of this repository is feature parity with the upstream project while providing a first-class experience for Python applications and tooling.

Contents

• Features
• Installation
• Quick Start
• Normalization Reference
• Encoding Behaviour
• Options
• Advanced Usage
• Testing
• Project Structure
• Versioning & Compatibility
• Contributing
• License

Features

• Normalises native Python types (dicts, lists, dataclasses, sets, datetime, numeric edge cases, etc.) to a JSON-like value space before encoding.
• Produces the familiar Toon text format with support for inline arrays, tabular object arrays, and deeply nested structures.
• Configurable indentation, row delimiter (',', '|', '\t'), and optional length marker flag ([#N] style headers).
• Safe string quoting and escaping rules that match the upstream implementation.
• Pure-Python, dependency-free package targeting Python 3.8+.

Installation

pip install pytoon-encoder

Working from a clone of this repository? Install in editable mode:

pip install -e .

Quick Start

from pytoon import encode

payload = {
    "user": {
        "id": 123,
        "name": "Ada",
        "tags": ["reading", "gaming"],
        "active": True,
        "prefs": [],
    }
}

print(encode(payload))

Output:

user:
  id: 123
  name: Ada
  tags[2]: reading,gaming
  active: true
  prefs[0]:

Normalization Reference

PyTOON first normalises values into a JSON-compatible shape. The table below mirrors the upstream Toon rules:

Python value	Normalised result	Notes
None	None	Encodes as null.
bool, int, float	Same numeric/boolean value	Floats that are NaN, ±inf become None; -0.0 becomes 0.
str	Same string	Subject to quoting/escaping rules during encoding.
datetime, date	ISO-8601 string	Uses .isoformat().
set, frozenset	List of normalised elements	Order is the iteration order of the set.
list, tuple, other sequences (not bytes)	List of normalised elements	Preserves order.
dict, Mapping	Dict with stringified keys	Keys are coerced with str(key); values normalised recursively.
dataclass instances	Dict via dataclasses.asdict	Deep conversion, then recurses.
Unsupported objects, functions, generators	None	Matches behaviour of upstream encoder.

Encoding Behaviour

PyTOON selects the most legible format while preserving structure:

• Objects render as key: value lines in insertion order. Empty objects emit just key:.
• Arrays of primitives appear inline: tags[3]: a,b,c.
• Arrays of objects become tabular if every object shares identical primitive keys. Otherwise, items are rendered as - list entries.
• Arrays of arrays with primitive inner arrays become nested lists; mixed or non-primitive inner arrays fall back to expanded list items.
• Mixed arrays (primitives, objects, arrays combined) always degrade to list entries.
• Strings remain unquoted only if they contain no structural characters, delimiters, leading/trailing whitespace, or ambiguous literals ("true", "42", etc.). Otherwise, they are quoted and escaped.

See examples/basic_usage.py for ready-to-run scenarios.

Options

encode accepts an optional EncodeOptions dictionary that mirrors the TypeScript API:

from pytoon import encode, DELIMITERS

encode(
    {"items": [{"id": 1, "name": "Ada"}, {"id": 2, "name": "Bob"}]},
    {
        "indent": 4,
        "delimiter": DELIMITERS["pipe"],  # or ',' / '\t'
        "length_marker": "#",             # renders headers as [#N]
    },
)

Output:

items[#2|]{id|name}:
  1|Ada
  2|Bob

Option reference:

Option	Type	Default	Description
indent	int	2	Spaces per indentation level for nested structures.
delimiter	',', `'	', '\t'`	','
length_marker	'#' or False	False	When '#', emits headers like [#3]; helpful when the consumer expects marked lengths.

Advanced Usage

• Pre-normalisation: Import normalize_value from pytoon.normalize to convert data once, then reuse the normalised structure across multiple encodings or transport layers.
• Direct value encoding: pytoon.encoders.encode_value accepts a pre-normalised JSON value plus resolved options, allowing integration with custom line writers or alternative indentation strategies.
• Custom delimiters: The DELIMITERS constant exposes the supported delimiter characters. Pass alternate values (e.g. DELIMITERS["tab"]) to match TSV-style pipelines.
• Examples: The examples/ directory contains scripts that highlight default behaviour and option combinations. Extend these for domain-specific onboarding material.
• Automation: .github/workflows/ci.yml runs unit tests on every push and publishes tagged releases (v*) to PyPI once tests pass.

Testing

Tests use Python's built-in unittest framework:

python3 -m unittest discover -s tests

When porting new behaviour from toon, add corresponding tests here to keep parity strong.

Project Structure

• pytoon/ – Core encoder modules (constants, normalize, primitives, encoders, writer).
• tests/ – Unit tests covering primitives, objects, arrays, options, and edge cases.
• examples/ – Runnable scripts that demonstrate practical usage patterns.

Versioning & Compatibility

PyTOON targets Python 3.8+ and strives to remain aligned with the latest upstream toon behaviour. Breaking format changes follow upstream and will be clearly documented in release notes.

Contributing

Contributions are welcome! To get started:

1. Fork and clone the repository.
2. Create a virtual environment for Python 3.8 or newer.
3. Install in editable mode with dev extras: pip install -e .[dev].
4. Run python3 -m unittest discover -s tests before submitting a pull request.

License

PyTOON retains the licensing of the original toon project. Refer to LICENSE for details.