========= jsonlines ========= .. py:currentmodule:: jsonlines ``jsonlines`` is a Python library to simplify working with jsonlines_ and ndjson_ data. .. _jsonlines: http://jsonlines.org/ .. _ndjson: http://ndjson.org/ This data format is straight-forward: it is simply one valid JSON value per line, encoded using UTF-8. While code to consume and create such data is not that complex, it quickly becomes non-trivial enough to warrant a dedicated library when adding data validation, error handling, support for both binary and text streams, and so on. This small library implements all that (and more!) so that applications using this format do not have to reinvent the wheel. Features ======== * Sensible behaviour for most use cases * transparently handles ``str`` and ``bytes``, both for input and output * supports multiple JSON libraries, e.g. ``json`` (standard library), ``orjson``, ``ujson`` * transparently handles UTF-8 BOM (if present) * useful error messages * prevents gotchas, e.g. uses standard-compliant line breaking, unlike `str.splitlines`_ .. _str.splitlines: https://docs.python.org/3/library/stdtypes.html#str.splitlines * Convenient :py:func:`~jsonlines.open()` function * makes simple cases trivial to write * takes a file name and a mode * returns either a :py:class:`~jsonlines.Reader` or :py:class:`~jsonlines.Writer` instance * can be used as a context manager * Flexible :py:class:`~jsonlines.Reader` * wraps a file-like object or any other iterable yielding lines * can read lines directly via the :py:meth:`~jsonlines.Reader.read()` method * can be used as an iterator, either directly or via the :py:meth:`~jsonlines.Reader.iter()` method * can validate data types, including `None` checks * can skip invalid lines during iteration * provides decent error messages * can be used as a context manager * allows complete control over decoding using a custom ``loads`` callable * Flexible :py:class:`~jsonlines.Writer` * wraps a file-like object * can produce compact output * can sort keys (deterministic output) * can flush the underlying stream after each write * can be used as a context manager * allows complete control over encoding using a custom ``dumps`` callable Installation ============ :: pip install jsonlines The supported Python versions are 3.8+. User guide ========== Import the ``jsonlines`` module to get started: .. code-block:: python import jsonlines The convenience function :py:func:`jsonlines.open()` takes a file name and returns either a reader or writer, making simple cases extremely simple:: with jsonlines.open('input.jsonl') as reader: for obj in reader: ... with jsonlines.open('output.jsonl', mode='w') as writer: writer.write(...) A :py:class:`Reader` typically wraps a file-like object:: fp = io.BytesIO(...) # readable file-like object reader = jsonlines.Reader(fp) first = reader.read() second = reader.read() reader.close() fp.close() Instead of a file-like object, any iterable yielding JSON encoded strings can be provided:: lines = ['1', '2', '3'] reader = jsonlines.Reader(lines) While the :py:meth:`Reader.read` method can be used directly, it is often more convenient to use iteration:: for obj in reader: ... Custom iteration flags, such as type checks, can be specified by calling :py:meth:`Reader.iter()` instead:: for obj in reader.iter(type=dict, skip_invalid=True): ... A :py:class:`Writer` wraps a file-like object, and can write a single object, or multiple objects at once:: fp = io.BytesIO() # writable file-like object writer = jsonlines.Writer(fp) writer.write(...) writer.write_all([ ..., ..., ..., ]) writer.close() fp.close() Both readers and writers can be used as a context manager, in which case they will be closed automatically. Note that this will not close a passed-in file-like object since that object’s life span is controlled by the calling code. Example:: fp = io.BytesIO() # file-like object with jsonlines.Writer(fp) as writer: writer.write(...) fp.close() Note that the :py:func:`jsonlines.open()` function *does* close the opened file, since the open file is not explicitly opened by the calling code. That means no ``.close()`` is needed there:: with jsonlines.open('input.jsonl') as reader: ... This should be enough to get started. See the API docs below for more details. API === .. autofunction:: jsonlines.open .. autoclass:: jsonlines.Reader :members: :inherited-members: .. autoclass:: jsonlines.Writer :members: :inherited-members: .. autoclass:: jsonlines.Error :members: .. autoclass:: jsonlines.InvalidLineError :members: Contributing ============ The source code and issue tracker for this package can be found on GitHub: https://github.com/wbolster/jsonlines Version history =============== * 4.0.0, released at 2023-09-01 * use ‘orjson’ or ‘ujson’ for reading if available (`#81 `_) * drop support for end-of-life Python versions; this package is now Python 3.8+ only. (`#80 `_, `#80 `_) * 3.1.0, released at 2022-07-01 * Return number of chars/bytes written by :py:meth:`Writer.write()` and :py:meth:`~Writer.write_all()` (`#73 `_) * allow ``mode='x'`` in :py:func:`~jsonlines.open()` to open a file for exclusive creation (`#74 `_) * 3.0.0, released at 2021-12-04 * add type annotations; adopt mypy in strict mode (`#58 `_, `#62 `_) * ignore UTF-8 BOM sequences in various scenarios (`#69 `_) * support ``dumps()`` callables returning bytes again (`#64 `_) * add basic support for rfc7464 text sequences (`#61 `_) * drop support for ``numbers.Number`` in ``type=`` arguments (`#63 `_) * 2.0.0, released at 2021-01-04 * drop support for end-of-life Python versions; this package is now Python 3.6+ only. (`#54 `_, `#51 `_) * 1.2.0, released at 2017-08-17 * allow ``mode='a'`` in :py:func:`~jsonlines.open()` to allow appending to an existing file (`#31 `_) * 1.1.3, released at 2017-07-19 * fix incomplete iteration when given list containing empty strings (`#30 `_) * 1.1.2, released at 2017-06-26 * documentation tweaks * enable building universal wheels * 1.1.1, released at 2017-06-04 * include licensing information in sdist (`#27 `_) * doc tweaks * 1.1.0, released at 2016-10-07 * rename first argument to :py:class:`Reader` since it is not required to be a file-like object * actually check that the reader/writer is not closed when performing operations * improved `repr()` output * doc tweaks * 1.0.0, released at 2016-10-05 * minimum Python versions are Python 3.4+ and Python 2.7+ * implemented lots of configuration options * add proper exceptions handling * add proper documentation * switch to semver * 0.0.1, released at 2015-03-02 * initial release with basic functionality License ======= .. include:: ../LICENSE.rst