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Kaydet (Commit) 3961f187 authored tarafından Georg Brandl's avatar Georg Brandl
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Fix JSON module docs.

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Doc/library/json.rst
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:mod:`json` JSON encoder and decoder
====================================
:mod:`json` --- JSON encoder and decoder
========================================
.. module:: json
:synopsis: encode and decode the JSON format
:synopsis: Encode and decode the JSON format.
.. moduleauthor:: Bob Ippolito <bob@redivi.com>
.. sectionauthor:: Bob Ippolito <bob@redivi.com>
.. versionadded:: 2.6
......@@ -10,8 +10,8 @@
JSON (JavaScript Object Notation) <http://json.org> is a subset of JavaScript
syntax (ECMA-262 3rd edition) used as a lightweight data interchange format.
:mod:`json` exposes an API familiar to uses of the standard library marshal and
pickle modules.
:mod:`json` exposes an API familiar to users of the standard library
:mod:`marshal` and :mod:`pickle` modules.
Encoding basic Python object hierarchies::
......@@ -74,7 +74,7 @@ Specializing JSON object decoding::
>>> json.loads('1.1', parse_float=decimal.Decimal)
Decimal('1.1')
Extending JSONEncoder::
Extending :class:`JSONEncoder`::
>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
......@@ -106,7 +106,7 @@ Using json.tool from the shell to validate and pretty-print::
.. note::
Note that the JSON produced by this module's default settings is a subset of
The JSON produced by this module's default settings is a subset of
YAML, so it may be used as a serializer for that as well.
......@@ -115,139 +115,104 @@ Basic Usage
.. function:: dump(obj, fp[, skipkeys[, ensure_ascii[, check_circular[, allow_nan[, cls[, indent[, separators[, encoding[, default[, **kw]]]]]]]]]])
Serialize *obj* as a JSON formatted stream to *fp* (a
``.write()``-supporting file-like object).
Serialize *obj* as a JSON formatted stream to *fp* (a ``.write()``-supporting
file-like object).
If *skipkeys* is ``True`` (It is ``False`` by default.), then ``dict`` keys
that are not basic types (``str``, ``unicode``, ``int``, ``long``,
``float``, ``bool``, ``None``) will be skipped instead of raising a
If *skipkeys* is ``True`` (default: ``False``), then dict keys that are not
of a basic type (:class:`str`, :class:`unicode`, :class:`int`, :class:`long`,
:class:`float`, :class:`bool`, ``None``) will be skipped instead of raising a
:exc:`TypeError`.
If *ensure_ascii* is ``False`` (It is ``True`` by default.), then the some
chunks written to *fp* may be ``unicode`` instances, subject to normal
Python ``str`` to ``unicode`` coercion rules. Unless ``fp.write()``
explicitly understands ``unicode`` (as in ``codecs.getwriter()``) this is
likely to cause an error.
If *ensure_ascii* is ``False`` (default: ``True``), then some chunks written
to *fp* may be :class:`unicode` instances, subject to normal Python
:class:`str` to :class:`unicode` coercion rules. Unless ``fp.write()``
explicitly understands :class:`unicode` (as in :func:`codecs.getwriter`) this
is likely to cause an error.
If *check_circular* is ``False``, then the circular reference check for
container types will be skipped and a circular reference will result in an
:exc:`OverflowError` (or worse).
If *check_circular* is ``False`` (default: ``True``), then the circular
reference check for container types will be skipped and a circular reference
will result in an :exc:`OverflowError` (or worse).
If *allow_nan* is ``False``, then it will be a :exc:`ValueError` to
serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in
strict compliance of the JSON specification, instead of using the JavaScript
equivalents (``NaN``, ``Infinity``, ``-Infinity``).
If *allow_nan* is ``False`` (default: ``True``), then it will be a
:exc:`ValueError` to serialize out of range :class:`float` values (``nan``,
``inf``, ``-inf``) in strict compliance of the JSON specification, instead of
using the JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``).
If *indent* is a non-negative integer, then JSON array elements and object
members will be pretty-printed with that indent level. An indent level of 0
will only insert newlines. ``None`` is the most compact representation.
will only insert newlines. ``None`` (the default) selects the most compact
representation.
If *separators* is an ``(item_separator, dict_separator)`` tuple then it
If *separators* is an ``(item_separator, dict_separator)`` tuple, then it
will be used instead of the default ``(', ', ': ')`` separators. ``(',',
':')`` is the most compact JSON representation.
*encoding* is the character encoding for str instances, default is UTF-8.
*default(obj)* is a function that should return a serializable version of
obj or raise :exc:`TypeError`. The default simply raises :exc:`TypeError`.
*obj* or raise :exc:`TypeError`. The default simply raises :exc:`TypeError`.
To use a custom :class:`JSONEncoder`` subclass (e.g. one that overrides the
``.default()`` method to serialize additional types), specify it with the
:meth:`default` method to serialize additional types), specify it with the
*cls* kwarg.
.. function:: dump(obj[, skipkeys[, ensure_ascii[, check_circular[, allow_nan[, cls[, indent[, separators[, encoding[, default[, **kw]]]]]]]]]])
.. function:: dumps(obj[, skipkeys[, ensure_ascii[, check_circular[, allow_nan[, cls[, indent[, separators[, encoding[, default[, **kw]]]]]]]]]])
Serialize *obj* to a JSON formatted ``str``.
Serialize *obj* to a JSON formatted :class:`str`.
If *skipkeys* is ``True`` (It is ``False`` by default.), then ``dict`` keys
that are not basic types (``str``, ``unicode``, ``int``, ``long``,
``float``, ``bool``, ``None``) will be skipped instead of raising a
:exc:`TypeError`.
If *ensure_ascii* is ``False``, then the return value will be a ``unicode``
instance subject to normal Python ``str`` to ``unicode`` coercion rules
instead of being escaped to an ASCII ``str``.
If *check_circular* is ``False``, then the circular reference check for
container types will be skipped and a circular reference will result in an
:exc:`OverflowError` (or worse).
If *allow_nan* is ``False``, then it will be a :exc:`ValueError` to
serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in
strict compliance of the JSON specification, instead of using the JavaScript
equivalents (``NaN``, ``Infinity``, ``-Infinity``).
If *ensure_ascii* is ``False``, then the return value will be a
:class:`unicode` instance. The other arguments have the same meaning as in
:func:`dump`.
If *indent* is a non-negative integer, then JSON array elements and object
members will be pretty-printed with that indent level. An indent level of 0
will only insert newlines. ``None`` is the most compact representation.
If *separators* is an ``(item_separator, dict_separator)`` tuple then it
will be used instead of the default ``(', ', ': ')`` separators. ``(',',
':')`` is the most compact JSON representation.
*encoding* is the character encoding for str instances, default is UTF-8.
*default(obj)* is a function that should return a serializable version of
obj or raise :exc:`TypeError`. The default simply raises :exc:`TypeError`.
To use a custom :class:`JSONEncoder`` subclass (e.g. one that overrides the
``.default()`` method to serialize additional types), specify it with the
*cls* kwarg.
.. function loads(s[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, **kw]]]]]]])
.. function load(fp[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, **kw]]]]]]])
Deserialize *s* (a ``str`` or ``unicode`` instance containing a JSON
Deserialize *fp* (a ``.read()``-supporting file-like object containing a JSON
document) to a Python object.
If *s* is a ``str`` instance and is encoded with an ASCII based encoding
other than utf-8 (e.g. latin-1) then an appropriate ``encoding`` name must be
specified. Encodings that are not ASCII based (such as UCS-2) are not allowed
and should be decoded to ``unicode`` first.
If the contents of *fp* are encoded with an ASCII based encoding other than
UTF-8 (e.g. latin-1), then an appropriate *encoding* name must be specified.
Encodings that are not ASCII based (such as UCS-2) are not allowed, and
should be wrapped with ``codecs.getreader(fp)(encoding)``, or simply decoded
to a :class:`unicode` object and passed to :func:`loads`.
*object_hook* is an optional function that will be called with the result of
any object literal decode (a ``dict``). The return value of ``object_hook``
will be used instead of the ``dict``. This feature can be used to implement
custom decoders (e.g. JSON-RPC class hinting).
any object literal decode (a :class:`dict`). The return value of
*object_hook* will be used instead of the :class:`dict`. This feature can be used
to implement custom decoders (e.g. JSON-RPC class hinting).
*parse_float*, if specified, will be called with the string of every JSON
float to be decoded. By default, this is equivalent to
``float(num_str)``. This can be used to use another datatype or parser for
JSON floats (e.g. decimal.Decimal).
float to be decoded. By default, this is equivalent to ``float(num_str)``.
This can be used to use another datatype or parser for JSON floats
(e.g. :class:`decimal.Decimal`).
*parse_int*, if specified, will be called with the string of every JSON int
to be decoded. By default this is equivalent to int(num_str). This can be
used to use another datatype or parser for JSON integers (e.g. float).
to be decoded. By default, this is equivalent to ``int(num_str)``. This can
be used to use another datatype or parser for JSON integers
(e.g. :class:`float`).
*parse_constant*, if specified, will be called with one of the following
strings: -Infinity, Infinity, NaN, null, true, false. This can be used to
raise an exception if invalid JSON numbers are encountered.
strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``, ``'null'``, ``'true'``,
``'false'``. This can be used to raise an exception if invalid JSON numbers
are encountered.
To use a custom :class:`JSONDecoder` subclass, specify it with the ``cls``
kwarg. Additional keyword arguments will be passed to the constructor of the
class.
.. function load(fp[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, **kw]]]]]]])
.. function loads(s[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, **kw]]]]]]])
Deserialize *fp* (a ``.read()``-supporting file-like object containing a JSON
Deserialize *s* (a :class:`str` or :class:`unicode` instance containing a JSON
document) to a Python object.
If the contents of *fp* is encoded with an ASCII based encoding other than
utf-8 (e.g. latin-1), then an appropriate ``encoding`` name must be
If *s* is a :class:`str` instance and is encoded with an ASCII based encoding
other than UTF-8 (e.g. latin-1), then an appropriate *encoding* name must be
specified. Encodings that are not ASCII based (such as UCS-2) are not
allowed, and should be wrapped with :func:`codecs.getreader(fp)(encoding)`,
or simply decoded to a ``unicode`` object and passed to ``loads()``
allowed and should be decoded to :class:`unicode` first.
*object_hook* is an optional function that will be called with the result of
any object literal decode (a ``dict``). The return value of *object_hook*
will be used instead of the ``dict``. This feature can be used to implement
custom decoders (e.g. JSON-RPC class hinting).
To use a custom :class:`JSONDecoder` subclass, specify it with the ``cls``
kwarg. Additional keyword arguments will be passed to the constructor of the
class.
The other arguments have the same meaning as in :func:`dump`.
Encoders and decoders
......@@ -255,7 +220,7 @@ Encoders and decoders
.. class:: JSONDecoder([encoding[, object_hook[, parse_float[, parse_int[, parse_constant[, strict]]]]]])
Simple JSON decoder
Simple JSON decoder.
Performs the following translations in decoding by default:
......@@ -282,42 +247,44 @@ Encoders and decoders
It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as their
corresponding ``float`` values, which is outside the JSON spec.
*encoding* determines the encoding used to interpret any ``str`` objects
decoded by this instance (utf-8 by default). It has no effect when decoding
``unicode`` objects.
*encoding* determines the encoding used to interpret any :class:`str` objects
decoded by this instance (UTF-8 by default). It has no effect when decoding
:class:`unicode` objects.
Note that currently only encodings that are a superset of ASCII work,
strings of other encodings should be passed in as ``unicode``.
Note that currently only encodings that are a superset of ASCII work, strings
of other encodings should be passed in as :class:`unicode`.
*object_hook*, if specified, will be called with the result of every JSON
object decoded and its return value will be used in place of the given
``dict``. This can be used to provide custom deserializations (e.g. to
:class:`dict`. This can be used to provide custom deserializations (e.g. to
support JSON-RPC class hinting).
*parse_float*, if specified, will be called with the string of every JSON
float to be decoded. By default this is equivalent to float(num_str). This
can be used to use another datatype or parser for JSON floats
(e.g. decimal.Decimal).
float to be decoded. By default, this is equivalent to ``float(num_str)``.
This can be used to use another datatype or parser for JSON floats
(e.g. :class:`decimal.Decimal`).
*parse_int*, if specified, will be called with the string of every JSON int
to be decoded. By default this is equivalent to int(num_str). This can be
used to use another datatype or parser for JSON integers (e.g. float).
to be decoded. By default, this is equivalent to ``int(num_str)``. This can
be used to use another datatype or parser for JSON integers
(e.g. :class:`float`).
*parse_constant*, if specified, will be called with one of the following
strings: -Infinity, Infinity, NaN, null, true, false. This can be used to
raise an exception if invalid JSON numbers are encountered.
strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``, ``'null'``, ``'true'``,
``'false'``. This can be used to raise an exception if invalid JSON numbers
are encountered.
.. method:: decode(s)
Return the Python representation of *s* (a ``str`` or ``unicode`` instance
containing a JSON document)
Return the Python representation of *s* (a :class:`str` or
:class:`unicode` instance containing a JSON document)
.. method:: raw_decode(s)
Decode a JSON document from *s* (a ``str`` or ``unicode`` beginning with a
JSON document) and return a 2-tuple of the Python representation and the
index in *s* where the document ended.
Decode a JSON document from *s* (a :class:`str` or :class:`unicode`
beginning with a JSON document) and return a 2-tuple of the Python
representation and the index in *s* where the document ended.
This can be used to decode a JSON document from a string that may have
extraneous data at the end.
......@@ -325,7 +292,7 @@ Encoders and decoders
.. class:: JSONEncoder([skipkeys[, ensure_ascii[, check_circular[, allow_nan[, sort_keys[, indent[, separators[, encoding[, default]]]]]]]]])
Extensible JSON <http://json.org> encoder for Python data structures.
Extensible JSON encoder for Python data structures.
Supports the following objects and types by default:
......@@ -348,7 +315,7 @@ Encoders and decoders
+-------------------+---------------+
To extend this to recognize other objects, subclass and implement a
``.default()`` method with another method that returns a serializable object
:meth:`default` method with another method that returns a serializable object
for ``o`` if possible, otherwise it should call the superclass implementation
(to raise :exc:`TypeError`).
......@@ -356,31 +323,32 @@ Encoders and decoders
attempt encoding of keys that are not str, int, long, float or None. If
*skipkeys* is ``True``, such items are simply skipped.
If *ensure_ascii* is ``True``, the output is guaranteed to be ``str`` objects
with all incoming unicode characters escaped. If *ensure_ascii* is
``False``, the output will be unicode object.
If *ensure_ascii* is ``True`` (the default), the output is guaranteed to be
:class:`str` objects with all incoming unicode characters escaped. If
*ensure_ascii* is ``False``, the output will be a unicode object.
If *check_circular* is ``True`` (the default), then lists, dicts, and custom
encoded objects will be checked for circular references during encoding to
prevent an infinite recursion (which would cause an :exc:`OverflowError`).
Otherwise, no such check takes place.
If *allow_nan* is ``True`` (the default), then ``NaN``, ``Infinity``, and ``-Infinity``
will be encoded as such. This behavior is not JSON specification compliant,
but is consistent with most JavaScript based encoders and decoders.
Otherwise, it will be a :exc:`ValueError` to encode such floats.
If *allow_nan* is ``True`` (the default), then ``NaN``, ``Infinity``, and
``-Infinity`` will be encoded as such. This behavior is not JSON
specification compliant, but is consistent with most JavaScript based
encoders and decoders. Otherwise, it will be a :exc:`ValueError` to encode
such floats.
If *sort_keys* is ``True`` (the default), then the output of dictionaries
will be sorted by key; this is useful for regression tests to ensure that
JSON serializations can be compared on a day-to-day basis.
If *indent* is a non-negative integer (It is ``None`` by default.), then JSON
If *indent* is a non-negative integer (it is ``None`` by default), then JSON
array elements and object members will be pretty-printed with that indent
level. An indent level of 0 will only insert newlines. ``None`` is the most
compact representation.
If specified, *separators* should be a (item_separator, key_separator) tuple.
The default is ``(', ', ': ')``. To get the most compact JSON
If specified, *separators* should be an ``(item_separator, key_separator)``
tuple. The default is ``(', ', ': ')``. To get the most compact JSON
representation, you should specify ``(',', ':')`` to eliminate whitespace.
If specified, *default* is a function that gets called for objects that can't
......@@ -423,9 +391,7 @@ Encoders and decoders
.. method:: iterencode(o)
Encode the given object, *o*, and yield each string representation as
available.
For example::
available. For example::
for chunk in JSONEncoder().iterencode(bigobject):
mysocket.write(chunk)
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