The Project Structure

Throughout this example we will assume the project structure:

|my_project_folder
|---|apg-py-main.zip
    |my_project
    |---__init__.py
    |---dynamic.py
    |---grammar.abnf
    |---static.py

All commands will be executed from the my_project_folder directory. The content of the files will be presented and explained as we go.

Installation

Make sure the PyPI version of apg-py is not installed. Otherwise it will override the local GitHub version.

> pip uninstall apg-py

Install the GitHub version of apg-py and make sure it is working.

> unzip apg-py-main.zip
> cp -r apg-py-main/apg_py .
> python3 apg_py --version

A Dynamic Generator with Parsing

The dynamic.py file should look like this.

import sys
import os
sys.path.append(os.getcwd()) # required to find apg_py
from apg_py.lib import utilities as util
from apg_py.lib.parser import Parser
from apg_py.api.api import Api
abnf = 'S = "a" S / "y"\n'
input = 'aaay'
api = Api()
grammar = api.generate(abnf)
if(api.errors):
    print('\n1) Grammar Errors')
    print(api.display_errors())
    exit()
parser = Parser(grammar)
result = parser.parse(utils.string_to_tuple(input))
print('\n1) Parser Result')
print(result)

Execute the command:

> python3 my_project/dynamic.py

You should see the results of a successful parse.

1) Parser Result
            success: True
              state: 101
              STATE: MATCH
       input_length: 4
          sub_begin: 0
            sub_end: 4
         sub_length: 4
      phrase_length: 4
  max_phrase_length: 4
          node_hits: 17
     max_tree_depth: 13

A Parsing from a Pre-Generated Grammar

Let's now do the same project except that we will generate the grammar object using the stand-alone generator. The ABNF grammar syntax file, grammar.abnf, is simply,

S = "a" S / "y"

(Make sure the line ends with a line feed.)

To convert this to the grammar object file grammar.py:

> python3 apg_py --input my_project/grammar.abnf

You should see the output

grammar object written to file my_project/grammar.py

The static.py file should look like,

import sys
import os
sys.path.append(os.getcwd()) # required to find apg_py
from apg_py.lib import utilities as utils
from apg_py.lib.parser import Parser
import grammar
print('The ABNF Syntax')
print(grammar.to_string())
input = 'aaay'
parser = Parser(grammar)
result = parser.parse(utils.string_to_tuple(input))
print('\n1) Parser Result')
print(result)

Now execute the static parser with,

> python3 my_project/static.py

The output should look like,

The ABNF Syntax
S = "a" S / "y"

1. Parser Result
    success: True
    state: 101
    STATE: MATCH
    input_length: 4
    sub_begin: 0
    sub_end: 4
    sub_length: 4
    phrase_length: 4
    max_phrase_length: 4
    node_hits: 17
    max_tree_depth: 13