Implemented PEP 405 (Python virtual environments).
diff --git a/Lib/idlelib/EditorWindow.py b/Lib/idlelib/EditorWindow.py
index c32064d..344f35d 100644
--- a/Lib/idlelib/EditorWindow.py
+++ b/Lib/idlelib/EditorWindow.py
@@ -120,7 +120,7 @@
 
     def __init__(self, flist=None, filename=None, key=None, root=None):
         if EditorWindow.help_url is None:
-            dochome =  os.path.join(sys.prefix, 'Doc', 'index.html')
+            dochome =  os.path.join(sys.base_prefix, 'Doc', 'index.html')
             if sys.platform.count('linux'):
                 # look for html docs in a couple of standard places
                 pyver = 'python-docs-' + '%s.%s.%s' % sys.version_info[:3]
@@ -131,13 +131,13 @@
                     dochome = os.path.join(basepath, pyver,
                                            'Doc', 'index.html')
             elif sys.platform[:3] == 'win':
-                chmfile = os.path.join(sys.prefix, 'Doc',
+                chmfile = os.path.join(sys.base_prefix, 'Doc',
                                        'Python%s.chm' % _sphinx_version())
                 if os.path.isfile(chmfile):
                     dochome = chmfile
             elif macosxSupport.runningAsOSXApp():
                 # documentation is stored inside the python framework
-                dochome = os.path.join(sys.prefix,
+                dochome = os.path.join(sys.base_prefix,
                         'Resources/English.lproj/Documentation/index.html')
             dochome = os.path.normpath(dochome)
             if os.path.isfile(dochome):