pyang

Pyang is an open‑source command‑line tool and Python library for working with YANG data models. It validates YANG modules against the YANG 1.1 and 1.1.1 specifications, reporting syntax errors, unresolved references, and other inconsistencies. In addition to validation, pyang can convert YANG models into a variety of output formats such as HTML documentation, PDF, RDF, and Python or Java code. The library can be imported into other Python programs, allowing developers to embed YANG processing into custom network automation workflows.

The tool supports a plugin architecture that lets developers extend its functionality. Standard plugins provide extra linting checks, a “diff” mode that shows changes between modules, and a “cluster” mode that merges multiple YANG modules into a unified namespace. Users can also write custom plugins to generate data structures for specific programming languages or to interface with network management protocols like NETCONF.

Pyang was originally written by Stefano Mari and is maintained as part of the open‑source community. The project is hosted on GitHub, where contributors submit bug fixes, new features, and compatibility patches. Pyang is widely used in research, industry and open‑source projects that require robust YANG support, including the OpenDaylight network controller and various embedded network devices. The tool is released under the BSD 3‑clause license, enabling free use in both open‑source and commercial environments.