# Changelog

This changelog is generated automatically from [GitHub Releases](https://github.com/posit-dev/py-yaml12/releases).


# yaml12 0.2.0

*2026-08-25* · [GitHub](https://github.com/posit-dev/py-yaml12/releases/tag/v0.2.0)


## Formatting

- [format_yaml()](reference/format_yaml.html#yaml12.format_yaml) and [write_yaml()](reference/write_yaml.html#yaml12.write_yaml) now produce more human-readable YAML while preserving exact round trips:

  - The new integer `width` argument defaults to 80 columns and wraps long strings at safe word boundaries. Pass `None` to disable wrapping.

  - Strings are emitted without quotes when YAML 1.2 permits. Strings that the core schema would read as null, a boolean, or a number remain quoted, including arbitrary-sized decimal, octal, and hexadecimal integer strings.

  - Multiline strings use readable folded or literal block styles when possible. Paragraph breaks, leading whitespace, empty lines, trailing newlines, and embedded document markers round-trip unchanged. Other multiline strings use a quoted fallback.

- Mapping keys longer than YAML's 1,024-character simple-key limit now use explicit key syntax.

- Non-finite floats now use the canonical spellings `.Inf`, `-.Inf`, and `.NaN` while continuing to round-trip as floats.

- [write_yaml()](reference/write_yaml.html#yaml12.write_yaml) and `format_yaml(..., multi=True)` no longer add optional document end (`...`) markers. Written documents still begin with `---` and end with a newline.


## Parsing and file handling

- By default, [parse_yaml()](reference/parse_yaml.html#yaml12.parse_yaml) and [read_yaml()](reference/read_yaml.html#yaml12.read_yaml) now preserve tags in the `tag:yaml.org,2002:` namespace that are not converted to built-in Python values in a [Yaml](reference/Yaml.html#yaml12.Yaml) wrapper. Explicit handlers still run when supplied.

- The parser now accepts and ignores reserved directives such as `%***`, and treats indented `---` text as part of a multiline plain scalar.

- [write_yaml()](reference/write_yaml.html#yaml12.write_yaml) gains an `append` argument for adding complete YAML documents to a filesystem path. Its default behavior still replaces the file. [read_yaml()](reference/read_yaml.html#yaml12.read_yaml) and [write_yaml()](reference/write_yaml.html#yaml12.write_yaml) also expand paths beginning with `~` using `os.path.expanduser()`.


## Installation

- Prebuilt wheels now include Intel macOS, Windows ARM64, and CPython 3.14 free-threaded builds. Free-threading support is currently beta. Source builds now require Rust 1.83 or newer.