pyang is a YANG validator, transformator and code generator, written in python. It can be used to validate YANG modules for correctness, to transform YANG modules into other formats, and to write plugins to generate code from the modules.

YANG (RFC 7950) is a data modeling language for NETCONF (RFC 6241), developed by the IETF NETMOD WG.

This fork introduces a new option called --sid-extension which add extra information to the sid file to allow easier conversion between JSON and CBOR formats. If the "Type" key is present, the sid is associated to a YANG leaf and the value indicate the type present in the YANG Data Model. In case of union, the value is an array of all the types.

--sid-extension build also a key-mapping entry containing the sid of a list as the object key and the sids of the list's keys as values. This may be use to find elements without referring to the YANG Data Model.

it will add a "type" key in the leaf SID description (the absence of type indicate that the node is not a leaf). Type is either:

• the type used in the definition
• an array of type for union
• an object mapping enumeration number with enumeration value

a "key-mapping" object. keys are list SIDs and value lists in an array the key SIDs. Testing the presence of "key-mapping" in the JSON structure allows to check if the --sid-extension argument has been specified.

WARNING: This hack has been tested on YANG Data Model used by SCHC. There is no guaranty that it works in all YANG Data Models.

See Documentation.

• 1 PyPI

Pyang can be installed from PyPI:

# pip install pyang

• 2 Source

  git clone https://github.com/ltn22/pyang.git
  cd pyang
  python setup.py install
  (this might require root access)

To install in a different location, run:

  python setup.py install --prefix=/usr/local

If you do this, it is recommended to set the environment variable YANG_INSTALL to the prefix directory. This ensures that pyang will find standard YANG modules. In addition, make sure that PYTHONPATH is set to something as follows:

export PYTHONPATH=/usr/local/lib/python2.7/site-packages

or whatever version of python you are running.

Run locally without installing

export PATH=`pwd`/bin:$PATH
export MANPATH=`pwd`/man:$MANPATH
export PYTHONPATH=`pwd`:$PYTHONPATH
export YANG_MODPATH=`pwd`/modules:$YANG_MODPATH
export PYANG_XSLT_DIR=`pwd`/xslt
export PYANG_RNG_LIBDIR=`pwd`/schema

or:

source ./env.sh

pyang is compatible with the following IETF RFCs:

• RFC 6020: YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)
• RFC 6087: Guidelines for Authors and Reviewers of YANG Data Model Documents
• RFC 6110: Mapping YANG to Document Schema Definition Languages and Validating NETCONF Content
• RFC 6643: Translation of Structure of Management Information Version 2 (SMIv2) MIB Modules to YANG Modules
• RFC 7950: The YANG 1.1 Data Modeling Languages
• RFC 7952: Defining and Using Metadata with YANGs
• RFC 8040: RESTCONF Protocols
• RFC 8407: Guidelines for Authors and Reviewers of Documents Containing YANG Data Models
• RFC 8791: YANG Data Structure Extensions

• Validate YANG modules.
• Convert YANG modules to YIN, and YIN to YANG.
• Translate YANG data models to DSDL schemas, which can be used for validating various XML instance documents. See InstanceValidation.
• Generate UML diagrams from YANG models. See UMLOutput for an example.
• Generate compact tree representation of YANG models for quick visualization. See TreeOutput for an example.
• Generate a skeleton XML instance document from the data model.
• Schema-aware translation of instance documents encoded in XML to JSON and vice-versa. See XmlJson.
• Plugin framework for simple development of other outputs, such as code generation.

pyang -h

or

man pyang

• bin/ Executable scripts.

• pyang/ Contains the pyang library code.

• pyang/init.py Initialization code for the pyang library.

• pyang/context.py Defines the Context class, which represents a parsing session

• pyang/repository.py Defines the Repository class, which is used to access modules.

• pyang/syntax.py Generic syntax checking for YANG and YIN statements. Defines regular expressions for argument checking of core statements.

• pyang/grammar.py Generic grammar for YANG and YIN. Defines chk_module_statements() which validates a parse tree according to the grammar.

• pyang/statements.py Defines the generic Statement class and all validation code.

• pyang/yang_parser.py YANG tokenizer and parser.

• pyang/yin_parser.py YIN parser. Uses the expat library for XML parsing.

• pyang/types.py Contains code for checking built-in types.

• pyang/plugin.py Plugin API. Defines the class PyangPlugin which all plugins inherits from. All output handlers are written as plugins.

• pyang/plugins/ Directory where plugins can be installed. All plugins in this directory are automatically initialized when the library is initialized.

• pyang/translators/ Contains output plugins for YANG, YIN, and DSDL translation.

• xslt Contains XSLT style sheets for generating RELAX NG, Schematron and DSRL schemas and validating instance documents. Also included is the free implementation of ISO Schematron by Rick Jelliffe from http://www.schematron.com/ (files iso_schematron_skeleton_for_xslt1.xsl, iso_abstract_expand.xsl and iso_svrl_for_xslt1.xsl).

• schema Contains RELAX NG schemas and pattern libraries.