json-tstring

JSON 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="rfc8259")  # -> Python data
render_text(template, profile="rfc8259")  # -> JSON text
render_result(template, profile="rfc8259")  # -> RenderResult (.text + .data)

Type alias: JsonProfile = Literal["rfc8259"]

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, parsed into JSON nodes (keeping interpolation visible in values, keys, and string fragments), and rendered back to text or Python data. serde_json handles normalization.

Supported positions

• whole-value, object-key, quoted-key-fragment, and string-fragment interpolation
• bare fragments promoted to JSON strings
• nested arrays and objects, top-level values

Limits

• object keys must be str
• non-finite floats rejected
• values must be JSON-representable
• integers keep exact Python text (no silent float coercion)

Verify

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

See also

• Project README
• Backend support matrix