This is an example of making language/parsing support for popular JSON data-interchange format.

JSON grammar is given in json.tx. All examples are taken from json.org example page.

Test script json.py will instantiate JSON meta-model defined in json.tx file, export it to dot file for visualization purposes and than instantiate all examples. Each, JSON example file is also exported to dot. To run it use:

$ python json.py

Checking and visualization can also be done using textx command line tool and GraphViz dot tool.

For example:

$ textx visualize json.tx example1.json
Meta-model OK.
Model OK.
Generating 'json.tx.dot' file for meta-model.
To convert to png run 'dot -Tpng -O json.tx.dot'
Generating 'example1.json.dot' file for model.
To convert to png run 'dot -Tpng -O example1.json.dot'

$ dot -Tpng -O example1.json.dot

Note: This is just an example that textX can be used to parse arbitrary textual format/language not just to build DSLs. It is always better to use specialised parsers if exists. For the purpose of JSON parsing in Python use json module. It is optimized for that purpose and thus performance will be much better.