[Python-checkins] bpo-30550: Clarify JSON ordering guarantees (GH-15397)
Raymond Hettinger
webhook-mailer at python.org
Thu Aug 22 18:14:48 EDT 2019
https://github.com/python/cpython/commit/657008ea0336ff4f275ed3f0c2b6dd2e52de2bba
commit: 657008ea0336ff4f275ed3f0c2b6dd2e52de2bba
branch: master
author: Raymond Hettinger <rhettinger at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2019-08-22T15:14:42-07:00
summary:
bpo-30550: Clarify JSON ordering guarantees (GH-15397)
files:
M Doc/library/json.rst
diff --git a/Doc/library/json.rst b/Doc/library/json.rst
index b476c372370d..56c16f5d296a 100644
--- a/Doc/library/json.rst
+++ b/Doc/library/json.rst
@@ -120,6 +120,18 @@ See :ref:`json-commandline` for detailed documentation.
value) is also a subset of YAML 1.0 and 1.1. This module can thus also be
used as a YAML serializer.
+.. note::
+
+ This module's encoders and decoders preserve input and output order by
+ default. Order is only lost if the underlying containers are unordered.
+
+ Prior to Python 3.7, :class:`dict` was not guaranteed to be ordered, so
+ inputs and outputs were typically scrambled unless
+ :class:`collections.OrderedDict` was specifically requested. Starting
+ with Python 3.7, the regular :class:`dict` became order preserving, so
+ it is no longer necessary specify :class:`collections.OrderedDict` for
+ JSON generation and parsing.
+
Basic Usage
-----------
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