.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "examples/advanced/scan_json.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_examples_advanced_scan_json.py>`
        to download the full example code

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_examples_advanced_scan_json.py:


Extracting JSON payloads from arbitrary text with ``Lark.scan``
================================================================

Shows ``Lark.scan`` finding JSON objects and arrays embedded in text.
JSON has a recursive structure, which makes this task very hard for regex,
but straightforward for a parser.

The grammar and ``Transformer`` here are essentially the same as in
``examples/json_parser.py``.

.. GENERATED FROM PYTHON SOURCE LINES 12-85

.. code-block:: default


    from lark import Lark, Transformer, v_args


    example_text = r'''
    [2024-05-10 12:00:01] INFO  login: {"user": "alice", "tags": ["admin", "active"]}
    [2024-05-10 12:00:05] ERROR auth failed: {
        "user": "bob",
        "attempt": 3,
        "blocked": false,
        "reason": "rate-limited"
    }
    ... that was unexpected; checking next event ...
    [2024-05-10 12:00:12] INFO  cart updated: {
        "cart_id": 42,
        "items": [
            {"sku": "X1", "qty": 2, "price": 9.99},
            {"sku": "Y2", "qty": 1, "price": 14.5e1}
        ],
        "promo": null
    }
    [2024-05-10 12:00:18] INFO  batch: ["a", "b", "c"]
    [2024-05-10 12:00:30] DEBUG no payload
    '''


    json_grammar = r"""
        ?start: object | array

        ?value: object
              | array
              | string
              | SIGNED_NUMBER      -> number
              | "true"             -> true
              | "false"            -> false
              | "null"             -> null

        array  : "[" (value ("," value)*)? "]"
        object : "{" (pair ("," pair)*)? "}"
        pair   : string ":" value

        string : ESCAPED_STRING

        %import common.ESCAPED_STRING
        %import common.SIGNED_NUMBER
        %import common.WS

        %ignore WS
    """


    class TreeToJson(Transformer):
        @v_args(inline=True)
        def string(self, s):
            return s[1:-1].replace('\\"', '"')

        array = list
        pair = tuple
        object = dict
        number = v_args(inline=True)(float)

        null = lambda self, _: None
        true = lambda self, _: True
        false = lambda self, _: False


    parser = Lark(json_grammar, parser="lalr", transformer=TreeToJson())


    print(f"{'Range':<14}  Payload")
    print("-" * 90)
    for match in parser.scan(example_text):
        print(f"{str(match.range):<14}  {match.value!r}")


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.000 seconds)


.. _sphx_glr_download_examples_advanced_scan_json.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example




    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: scan_json.py <scan_json.py>`

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: scan_json.ipynb <scan_json.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_