IANA-BCP47

iana-bcp47 validates language tags using the grammar from RFC 5646 and the bundled IANA Language Subtag Registry. Validation is local and does not require a network connection.

Features

• Case-insensitive RFC 5646 syntax and ordering validation.
• Registered language, extlang, script, region, and variant subtags.
• Grandfathered and redundant tags.
• Extensions and private-use tags, including IANA private-use ranges.
• Deprecated subtags remain valid and include replacement guidance when IANA provides it.
• Python 3.11 through 3.14.

Extension payloads are checked against the generic RFC 5646 grammar. This package does not interpret extension-specific standards such as Unicode locale extension semantics. Registry Prefix values are retained as metadata and guidance; RFC 5646 does not make them a validity requirement.

Installation

pip install iana-bcp47

Usage

from iana_bcp47 import validate_bcp47

for tag in ["en-US", "EN-us", "zh-Hant-CN", "i-klingon", "x-private"]:
    valid, message = validate_bcp47(tag)
    print(tag, valid, message)

validate_bcp47(tag) returns (valid, message). Invalid input returns False and an error message; passing a non-string raises TypeError. The wording of descriptions and errors may evolve as the IANA registry changes.

The legacy dictionaries remain available from iana_bcp47.bcp47 and from the package root:

from iana_bcp47 import language_codes, region_codes

Data maintenance

The packaged registry date can be read from iana_bcp47._registry.get_registry().file_date. A scheduled GitHub Actions workflow checks IANA every Monday. When the snapshot changes, it updates the data, increments the package patch version, runs validation, and opens or refreshes an automation/iana-registry pull request. A maintainer reviews and merges that PR; a successful main CI run then publishes the new version through PyPI Trusted Publishing.

To inspect an update locally without modifying files:

python -m pip install -e ".[dev]"
python tools/update_registry.py --dry-run

Run the maintenance checks with:

ruff check .
ruff format --check .
pytest
python -m build
twine check dist/*
check-wheel-contents dist/*.whl

License

MIT. See LICENSE.