yaml-tstring

YAML rendering for PEP 750 t-strings. Parsing and rendering happen in Rust; this package is the Python wrapper.

Requires Python 3.14+.

This package depends on tstring-bindings, a native PyO3 extension. On supported platforms, install from prebuilt wheels. Other environments require a local Rust 1.94.0 toolchain build.

API

render_data(template, profile="1.2.2")  # -> Python data (list for multi-doc)
render_text(template, profile="1.2.2")  # -> YAML text
render_result(template, profile="1.2.2")  # -> RenderResult (.text + .data)

Type alias: YamlProfile = Literal["1.2.2"]

Parsed template structure is cached per process using template.strings + profile as the key.

How it works

The Python Template is converted to a Rust token stream and parsed by an interpolation-aware YAML scanner/parser. Block mappings, block sequences, flow collections, scalar styles, anchors, aliases, and tags are all parsed explicitly in Rust with interpolation nodes preserved. saphyr handles data materialization and normalization.

Supported positions

• mapping-key interpolation
• plain, single-quoted, double-quoted, and block scalar assembly
• anchor, alias, and tag interpolation (including verbatim !<...> tags)
• block and flow collections, multi-document streams
• directives, %TAG handles, explicit document markers
• merge keys, complex keys, trailing commas in flow collections
• YAML 1.2.2 escape sequences in double-quoted scalars

The full tested boundary is in the backend support matrix.

Limits

• non-finite floats rejected
• metadata fragments must be non-empty and whitespace-free
• integers keep exact Python text (no silent float coercion)
• values must be representable in the current YAML 1.2+ surface

Verify

uv sync --group dev
uv run --group dev pytest

See also

• Project README
• Backend support matrix