#16333: document a way to get rid of trailing whitespace when indent is used.

2 files changed, 12 insertions, 5 deletions

diff --git a/Lib/json/__init__.py b/Lib/json/__init__.py
index 86a7a3e..44f49c4 100644
--- a/Lib/json/__init__.py
+++ b/Lib/json/__init__.py
@@ -39,8 +39,8 @@ Compact encoding::
 Pretty printing::
 
     >>> import json
-    >>> s = json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4)
-    >>> print('\n'.join([l.rstrip() for l in  s.splitlines()]))
+    >>> print(json.dumps({'4': 5, '6': 7}, sort_keys=True,
+    ...                  indent=4, separators=(',', ': ')))
     {
         "4": 5,
         "6": 7
@@ -146,7 +146,9 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
     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.
+    representation.  Since the default item separator is ``', '``,  the
+    output might include trailing whitespace when ``indent`` is specified.
+    You can use ``separators=(',', ': ')`` to avoid this.
 
     If ``separators`` is an ``(item_separator, dict_separator)`` tuple
     then it will be used instead of the default ``(', ', ': ')`` separators.
@@ -207,7 +209,9 @@ def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
     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.
+    representation.  Since the default item separator is ``', '``,  the
+    output might include trailing whitespace when ``indent`` is specified.
+    You can use ``separators=(',', ': ')`` to avoid this.
 
     If ``separators`` is an ``(item_separator, dict_separator)`` tuple
     then it will be used instead of the default ``(', ', ': ')`` separators.
diff --git a/Lib/json/encoder.py b/Lib/json/encoder.py
index 75b7f49..e1ed21f 100644
--- a/Lib/json/encoder.py
+++ b/Lib/json/encoder.py
@@ -125,7 +125,10 @@ class JSONEncoder(object):
         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.
+        None is the most compact representation.  Since the default
+        item separator is ', ',  the output might include trailing
+        whitespace when indent is specified.  You can use
+        separators=(',', ': ') to avoid this.
 
         If specified, separators should be a (item_separator, key_separator)
         tuple.  The default is (', ', ': ').  To get the most compact JSON