Generating Python Classes

The lionweb package includes a CLI tool, lionweb-gen, to generate Python bindings (classes, language definitions, and deserializers) from LionWeb language definition files (JSON).

Installation

You typically create a Python virtual environment and install the package there:

python3 -m venv venv
source venv/bin/activate
pip install lionweb

CLI Usage

The general syntax for the generator is:

lionweb-gen [OPTIONS] LIONWEB_LANGUAGE OUTPUT

Arguments

• LIONWEB_LANGUAGE: Path to the existing LionWeb language file (JSON).
• OUTPUT: Path to the output directory where Python files will be generated.

Options

Option	Shorthand	Description
--dependencies	-d	Path to a LionWeb language file necessary to use as dependencies to open the target languages. Can be specified multiple times.
--language-packages	--lp	Maps a language ID or name to the Python package that provides it. Format: LANG=PACKAGE (e.g., MyLang=myapp.lang).
--primitive-types	--pt	Maps a primitive type ID or name to the Python type that provides it. Format: PRIMITIVE_TYPE=QUALIFIED_NAME (e.g., String=str).
--lionweb-version	--lwv	LionWeb version to use for processing. Defaults to 2023.1.
--help		Show the help message and exit.

Examples

SysML2 Generation Example

Below is an example of generating bindings for SysML2, utilizing dependencies and type mappings.

1. Clean previous generation

   rm -Rf sysml2py/kerml/
   rm -Rf sysml2py/sysml/
   rm -Rf sysml2py/types/

2. Generate Base Types

   lionweb-gen ../models/types_lionweb.json sysml2py/types

3. Generate KerML (depends on types)

   lionweb-gen ../models/kerml_lionweb_lionweb.json \
     -d ../models/types_lionweb.json \
     sysml2py/kerml \
     --lp types=sysml2py.types \
     --pt String=str --pt Boolean=bool --pt Integer=int --pt Real=float

4. Generate SysML (depends on types)

   lionweb-gen ../models/SysML_lionweb_lionweb.json \
     -d ../models/types_lionweb.json \
     sysml2py/sysml \
     --lp types=sysml2py.types \
     --pt String=str --pt Boolean=bool --pt Integer=int --pt Real=float

Generated Output

The tool generates the following files in the specified output directory:

• language.py: Defines the Language instance, including all Concepts, Interfaces, Enumerations, and their features.
• deserializer.py: Contains the register_deserializers function to register custom deserializers for the language's concepts.
• __init__.py: Exports all generated classes for easy importing.
• Node Classes: A separate Python file for every Concept, Interface, and Enumeration (e.g., my_concept.py). These classes include type-hinted getters and setters for properties, containments, and references.