Issue #14570: Document json sort_keys parameter properly.

Patch by Chris Rebert.

Doc/library/json.rst

@@ -116,7 +116,10 @@ Using json.tool from the shell to validate and pretty-print::
 Basic Usage
 -----------
 
-.. function:: dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, **kw)
+.. function:: dump(obj, fp, skipkeys=False, ensure_ascii=True, \
+                   check_circular=True, allow_nan=True, cls=None, \
+                   indent=None, separators=None, default=None, \
+                   sort_keys=False, **kw)
 
    Serialize *obj* as a JSON formatted stream to *fp* (a ``.write()``-supporting
    :term:`file-like object`).
@@ -159,12 +162,18 @@ Basic Usage
    *default(obj)* is a function that should return a serializable version of
    *obj* or raise :exc:`TypeError`.  The default simply raises :exc:`TypeError`.
 
+   If *sort_keys* is ``True`` (default: ``False``), then the output of
+   dictionaries will be sorted by key.
+
    To use a custom :class:`JSONEncoder` subclass (e.g. one that overrides the
    :meth:`default` method to serialize additional types), specify it with the
    *cls* kwarg; otherwise :class:`JSONEncoder` is used.
 
 
-.. function:: dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, **kw)
+.. function:: dumps(obj, skipkeys=False, ensure_ascii=True, \
+                    check_circular=True, allow_nan=True, cls=None, \
+                    indent=None, separators=None, default=None, \
+                    sort_keys=False, **kw)
 
    Serialize *obj* to a JSON formatted :class:`str`.  The arguments have the
    same meaning as in :func:`dump`.

Lib/json/__init__.py

@@ -122,7 +122,7 @@ _default_encoder = JSONEncoder(
 
 def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
         allow_nan=True, cls=None, indent=None, separators=None,
-        default=None, **kw):
+        default=None, sort_keys=False, **kw):
     """Serialize ``obj`` as a JSON formatted stream to ``fp`` (a
     ``.write()``-supporting file-like object).
 
@@ -155,6 +155,9 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
     ``default(obj)`` is a function that should return a serializable version
     of obj or raise TypeError. The default simply raises TypeError.
 
+    If *sort_keys* is ``True`` (default: ``False``), then the output of
+    dictionaries will be sorted by key.
+
     To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
     ``.default()`` method to serialize additional types), specify it with
     the ``cls`` kwarg; otherwise ``JSONEncoder`` is used.
@@ -164,7 +167,7 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
     if (not skipkeys and ensure_ascii and
         check_circular and allow_nan and
         cls is None and indent is None and separators is None and
-        default is None and not kw):
+        default is None and not sort_keys and not kw):
         iterable = _default_encoder.iterencode(obj)
     else:
         if cls is None:
@@ -172,7 +175,7 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
         iterable = cls(skipkeys=skipkeys, ensure_ascii=ensure_ascii,
             check_circular=check_circular, allow_nan=allow_nan, indent=indent,
             separators=separators,
-            default=default, **kw).iterencode(obj)
+            default=default, sort_keys=sort_keys, **kw).iterencode(obj)
     # could accelerate with writelines in some versions of Python, at
     # a debuggability cost
     for chunk in iterable:
@@ -181,7 +184,7 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
 
 def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
         allow_nan=True, cls=None, indent=None, separators=None,
-        default=None, **kw):
+        default=None, sort_keys=False, **kw):
     """Serialize ``obj`` to a JSON formatted ``str``.
 
     If ``skipkeys`` is false then ``dict`` keys that are not basic types
@@ -213,6 +216,9 @@ def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
     ``default(obj)`` is a function that should return a serializable version
     of obj or raise TypeError. The default simply raises TypeError.
 
+    If *sort_keys* is ``True`` (default: ``False``), then the output of
+    dictionaries will be sorted by key.
+
     To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
     ``.default()`` method to serialize additional types), specify it with
     the ``cls`` kwarg; otherwise ``JSONEncoder`` is used.
@@ -222,14 +228,14 @@ def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
     if (not skipkeys and ensure_ascii and
         check_circular and allow_nan and
         cls is None and indent is None and separators is None and
-        default is None and not kw):
+        default is None and not sort_keys and not kw):
         return _default_encoder.encode(obj)
     if cls is None:
         cls = JSONEncoder
     return cls(
         skipkeys=skipkeys, ensure_ascii=ensure_ascii,
         check_circular=check_circular, allow_nan=allow_nan, indent=indent,
-        separators=separators, default=default,
+        separators=separators, default=default, sort_keys=sort_keys,
         **kw).encode(obj)