diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 4d6584b..86a6aa0 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1705,9 +1705,12 @@
         'CONTEXTMANAGERS': ('context-managers', 'with'),
     }
 
-    def __init__(self, input, output):
-        self.input = input
-        self.output = output
+    def __init__(self, input=None, output=None):
+        self._input = input
+        self._output = output
+
+    input  = property(lambda self: self._input or sys.stdin)
+    output = property(lambda self: self._output or sys.stdout)
 
     def __repr__(self):
         if inspect.stack()[1][3] == '?':
@@ -1884,7 +1887,7 @@
 for modules whose descriptions contain the word "spam".
 ''')
 
-help = Helper(sys.stdin, sys.stdout)
+help = Helper()
 
 class Scanner:
     """A generic tree iterator."""