ast_example.py

import ast
import sys

import inflection


class TransformDeclaredAttr(ast.NodeTransformer):
    def visit_FunctionDef(self, node: ast.FunctionDef):
        if 'declared_attr' in [dec.id for dec in node.decorator_list]:
            assert len(node.body) == 1
            assert isinstance(node.body[0], ast.Return)
            call = node.body[0].value
            assert isinstance(call, ast.Call)
            assert len(call.args) == 2
            assert isinstance(call.args[1], ast.Call)

            new_name = inflection.underscore(node.name).lower()

            return ast.Assign(
                targets=[ast.Name(id=new_name, ctx=ast.Store())],
                value=call.args[1],
                lineno=node.lineno,
            )

        return self.generic_visit(node)


with open(sys.argv[1]) as file:
    tree = ast.parse(file.read())

new_tree = TransformDeclaredAttr().visit(tree)
print(ast.unparse(new_tree))