diff -r 1d515909e624 Doc/library/json.rst
--- a/Doc/library/json.rst	Wed Nov 28 02:47:45 2012 -0800
+++ b/Doc/library/json.rst	Wed Nov 28 17:59:08 2012 +0200
@@ -42,7 +42,8 @@
 Pretty printing::
 
     >>> import json
-    >>> print(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))
+    >>> print(json.dumps({'4': 5, '6': 7}, sort_keys=True,
+    ...     indent=4, separators=(',', ': ')))
     {
         "4": 5,
         "6": 7
@@ -155,6 +156,11 @@
    .. versionchanged:: 3.2
       Allow strings for *indent* in addition to integers.
 
+   .. note::
+
+      Use ``separators=(',', ': ')`` instead the default *separators* to supress
+      an extra space preciding the newline.
+
    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.
@@ -393,6 +399,11 @@
    .. versionchanged:: 3.2
       Allow strings for *indent* in addition to integers.
 
+   .. note::
+
+      Use ``separators=(',', ': ')`` instead the default *separators* to supress
+      an extra space preciding the newline.
+
    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.
diff -r 1d515909e624 Lib/json/tool.py
--- a/Lib/json/tool.py	Wed Nov 28 02:47:45 2012 -0800
+++ b/Lib/json/tool.py	Wed Nov 28 17:59:08 2012 +0200
@@ -29,7 +29,7 @@
         obj = json.load(infile)
     except ValueError as e:
         raise SystemExit(e)
-    json.dump(obj, outfile, sort_keys=True, indent=4)
+    json.dump(obj, outfile, sort_keys=True, indent=4, separators=(',', ': '))
     outfile.write('\n')