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.. -*- coding: utf-8 -*-
.. :Project: python-rapidjson -- Encoder class documentation
.. :Author: Lele Gaifax <lele@metapensiero.it>
.. :License: MIT License
.. :Copyright: © 2017, 2018, 2019, 2020 Lele Gaifax
..
===============
Encoder class
===============
.. currentmodule:: rapidjson
.. testsetup::
from rapidjson import Decoder, Encoder, BM_NONE, IM_ONLY_LISTS, MM_ONLY_DICTS
.. class:: Encoder(skip_invalid_keys=False, ensure_ascii=True, write_mode=WM_COMPACT, \
indent=4, sort_keys=False, number_mode=None, datetime_mode=None, \
uuid_mode=None, bytes_mode=BM_UTF8, iterable_mode=IM_ANY_ITERABLE, \
mapping_mode=MM_ANY_MAPPING)
Class-based :func:`dumps`\ -like functionality.
:param bool skip_invalid_keys: whether invalid :class:`dict` keys :ref:`will be skipped
<skip-invalid-keys>`
:param bool ensure_ascii: whether the output should contain :ref:`only ASCII
characters <ensure-ascii>`
:param int write_mode: enable particular :ref:`pretty print <write-mode>` behaviors
:param indent: either an integer, the indentation width, or a string, that will be used
as line separator, when `write_mode` is not :data:`WM_COMPACT`
:param bool sort_keys: whether dictionary keys should be :ref:`sorted
alphabetically <sort-keys>`
:param int number_mode: enable particular :ref:`behaviors in handling numbers
<dumps-number-mode>`
:param int datetime_mode: how should :ref:`datetime, time and date instances be handled
<dumps-datetime-mode>`
:param int uuid_mode: how should :ref:`UUID instances be handled <dumps-uuid-mode>`
:param int bytes_mode: how should :ref:`bytes instances be handled <dumps-bytes-mode>`
:param int iterable_mode: how should `iterable` values be handled
:param int mapping_mode: how should `mapping` values be handled
.. rubric:: Attributes
.. attribute:: bytes_mode
:type: int
How bytes values should be treated.
.. attribute:: datetime_mode
:type: int
Whether and how datetime values should be encoded.
.. attribute:: ensure_ascii
:type: bool
Whether the output should contain only ASCII characters.
.. attribute:: indent_char
:type: str
What will be used as end-of-line character.
.. attribute:: indent_count
:type: int
The indentation width.
.. attribute:: iterable_mode
:type: int
Whether `iterables` will be generically encoded as ``JSON`` arrays or not.
.. attribute:: mapping_mode
:type: int
Whether `mappings` will be generically encoded as ``JSON`` objects or not.
.. attribute:: number_mode
:type: int
The encoding behavior with regards to numeric values.
.. attribute:: skip_invalid_keys
:type: bool
Whether invalid keys shall be skipped.
.. note:: `skip_invalid_keys` is a backward compatible alias of new
``MM_SKIP_NON_STRING_KEYS`` :ref:`mapping mode <mapping_mode>`.
.. attribute:: sort_keys
:type: bool
Whether dictionary keys shall be sorted alphabetically.
.. note:: `sort_keys` is a backward compatible alias of new ``MM_SORT_KEYS``
:ref:`mapping mode <mapping_mode>`.
.. attribute:: uuid_mode
:type: int
Whether and how UUID values should be encoded
.. attribute:: write_mode
:type: int
Whether the output should be pretty printed or not.
.. rubric:: Methods
.. method:: __call__(obj, stream=None, *, chunk_size=65536)
:param obj: the value to be encoded
:param stream: a *file-like* instance
:param int chunk_size: write the stream in chunks of this size at a time
:returns: a string with the ``JSON`` encoded `value`, when `stream` is ``None``
When `stream` is specified, the encoded result will be written there, possibly in
chunks of `chunk_size` bytes at a time, and the return value will be ``None``.
.. method:: default(value)
:param value: the Python value to be encoded
:returns: a *JSON-serializable* value
If implemented, this method is called whenever the serialization machinery finds a
Python object that it does not recognize: if possible, the method should returns a
*JSON encodable* version of the `value`, otherwise raise a :exc:`TypeError`:
.. doctest::
>>> class Point:
... def __init__(self, x, y):
... self.x = x
... self.y = y
...
>>> point = Point(1,2)
>>> Encoder()(point)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: <__main__.Point object at …> is not JSON serializable
>>> class PointEncoder(Encoder):
... def default(self, obj):
... if isinstance(obj, Point):
... return {'x': obj.x, 'y': obj.y}
... else:
... raise TypeError('%r is not JSON serializable' % obj)
...
>>> pe = PointEncoder(sort_keys=True)
>>> pe(point)
'{"x":1,"y":2}'
When you want to treat your :class:`bytes` instances in a special way, you can use
:data:`BM_NONE` together with this method:
.. doctest::
>>> class HexifyBytes(Encoder):
... def default(self, obj):
... if isinstance(obj, bytes):
... return obj.hex()
... else:
... return obj
...
>>> small_numbers = bytes([1, 2, 3])
>>> hb = HexifyBytes(bytes_mode=BM_NONE)
>>> hb(small_numbers)
'"010203"'
Likewise, when you want full control on how an `iterable` such as a ``tuple`` should
be encoded, you can use :data:`IM_ONLY_LISTS` and implement a suitable ``default()``
method:
.. doctest::
>>> from time import localtime, struct_time
>>> class ObjectifyStructTime(Encoder):
... def default(self, obj):
... if isinstance(obj, struct_time):
... return {'__class__': 'time.struct_time', '__init__': list(obj)}
... else:
... raise ValueError('%r is not JSON serializable' % obj)
...
>>> obst = ObjectifyStructTime(iterable_mode=IM_ONLY_LISTS)
>>> obst(localtime()) # doctest: +SKIP
'[2020,11,28,19,55,40,5,333,0]'
Similarly, when you want full control on how a `mapping` other than plain ``dict``
should be encoded, you can use :data:`MM_ONLY_DICTS` and implement a ``default()``
method:
.. doctest::
>>> from collections import OrderedDict
>>> class ObjectifyOrderedDict(Encoder):
... def default(self, obj):
... if isinstance(obj, OrderedDict):
... return {'__class__': 'collections.OrderedDict',
... '__init__': list(obj.items())}
... else:
... raise ValueError('%r is not JSON serializable' % obj)
...
>>> ood = ObjectifyOrderedDict(mapping_mode=MM_ONLY_DICTS)
>>> ood(OrderedDict((('a', 1), ('b', 2))))
'{"__class__":"collections.OrderedDict","__init__":[["a",1],["b",2]]}'
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