MegaIng/tree_ql

TreeQL: a query language for Tree structures

What

A query language for Tree structures, modeled after XPath.

Provides a concrete implementation for Lark parse trees. Can be extended to other tree structures.

Example:

from tree_ql import LarkQuery
from lark  import Lark
from pathlib  import Path
from tests.test_data.python_indenter import PythonIndenter

parser = Lark.open(Path(__file__).parent / 'tests' /'test_data'/'python3.lark', start = 'file_input', postlex = PythonIndenter(), parser = 'lalr')
with open(Path(__file__), 'r') as f:
    tree = parser.parse(f.read() +'\n')

query = LarkQuery('/import_stmt/import_from//leaf()')
result = query.execute(tree)
print(result)

Prints:

['tree_ql', 'lark', 'pathlib', 'tests', 'test_data', 'python_indenter']

Full grammar is here.

Install via pip:

pip install git+https://github.com/adbancroft/tree_ql.git

Why

Lark parse trees can already be navigated using:

1. The provided hooks for visitation & transformation. These are comprehensive and type safe, but result in a lot of code if you need to query the tree in many different ways.

2. Native Python approaches such as list comprehensions. Simple to use if processing a limited set of nodes (such a Tree.children), but complicated to write to be fully aware of the entire tree.

This module provides a 3rd method, positioned between these 2. It takes account of the tree hierarchy while providing the flexibility of a query language.