Installation

Create a virtual environment:

python -m venv venv

Activate it (on Windows):

venv/Scripts/activate

… or on Unix:

source venv/bin/activate

Install the dependencies:

pip3 install express-schema

You can now use the modules express_schema.parse (see “Usage” section below) or run express-schema (see --help section below).

Usage

The Abstract Syntax Tree and parsing functionality lives in express_schema.parse module.

Example:

>>> import express_schema.parse as parse
>>>
>>> # Define a simple EXPRESS schema as a string
>>> schema_text = '''SCHEMA SimpleExample;
...
... ENTITY Person;
...   name : STRING;
...   age : INTEGER;
... END_ENTITY;
...
... END_SCHEMA;'''
>>>
>>> # Parse the schema
>>> schema, errors = parse.parse(schema_text)
>>>
>>> # Check for parsing errors
>>> if errors is not None:
...     print("Parsing errors occurred:")
...     for error in errors:
...         print(
...             f"  Line {error.line}, Column {error.column}: "
...             f"{error.message}"
...         )
... else:
...     print("Schema parsed successfully!")
...     print(f"Schema name: {schema.identifier}")
...     print(f"Number of entities: {len(schema.entity_declarations)}")
...
...     # Dump the parsed schema back to text
...     dumped_text = parse.dump(schema)
...     print("Dumped schema:")
...     print(dumped_text)
Schema parsed successfully!
Schema name: SimpleExample
Number of entities: 1
Dumped schema:
Schema(
  position=1:1,
  identifier='SimpleExample',
  reference_clauses=[],
  use_clauses=[],
  constant_definitions=[],
  entity_declarations=[EntityDeclaration(
      position=3:1,
      identifier='Person',
      explicit_clauses=[
          ExplicitAttributeDefinition(
            position=4:3,
            attributes=[NameRef(
                position=4:3,
                identifier='name'
              )],
            optional=False,
            type_selection=StringType(
                position=4:10,
                fixed=False
              )
          ),
          ExplicitAttributeDefinition(
            position=5:3,
            attributes=[NameRef(
                position=5:3,
                identifier='age'
              )],
            optional=False,
            type_selection=IntegerType(
                position=5:9
              )
          )
        ],
      derive_clauses=[],
      inverse_clauses=[],
      unique_rules=[],
      domain_rules=[]
    )],
  function_declarations=[],
  procedure_declarations=[],
  type_declarations=[],
  rule_declarations=[]
)

If, for some reason, you only want to tokenize and not parse the schema, you can use express_schema.lex module.

Example:

>>> import express_schema.lex as lex
>>>
>>> # Define a simple EXPRESS schema text to tokenize
>>> schema_text = '''SCHEMA Example;
... ENTITY Person;
...   name : STRING;
... END_ENTITY;
... END_SCHEMA;'''
>>>
>>> # Tokenize the schema
>>> tokens, success = lex.lex(schema_text)
>>>
>>> # Check if tokenization was successful
>>> if success:
...     print("Tokenization successful!")
...     print(f"Number of tokens: {len(tokens)}")
...     print("First few tokens:")
...     for token in tokens[:5]:
...         print(
...             f"  {token.kind.name} at {token.position}: "
...             f"{token.text!r}"
...         )
... else:
...     print("Tokenization failed!")
Tokenization successful!
Number of tokens: 14
First few tokens:
  SCHEMA at 1:1: 'SCHEMA'
  IDENTIFIER at 1:8: 'Example'
  SEMI at 1:15: ';'
  ENTITY at 2:1: 'ENTITY'
  IDENTIFIER at 2:8: 'Person'

--help

usage: express-schema [-h] --schema SCHEMA [--version]

Parse EXPRESS Schema (ISO 10303-11) and print the Abstract Syntax Tree.

options:
  -h, --help       show this help message and exit
  --schema SCHEMA  Path to the EXPRESS schema file
  --version        show the current version and exit

Contributing

See CONTRIBUTING.rst.

Change Log