Index: Doc/library/urlparse.rst
===================================================================
--- Doc/library/urlparse.rst	(revision 64056)
+++ Doc/library/urlparse.rst	(working copy)
@@ -52,6 +52,23 @@
       >>> o.geturl()
       'http://www.cwi.nl:80/%7Eguido/Python.html'
 
+   If the scheme value is not specified, urlparse following the syntax
+   specifications from RFC 1808, expects the netloc value to start with '//',
+   Otherwise, it is not possible to distinguish between net_loc and path
+   component and would classify the indistinguishable component as path as in
+   a relative url.
+
+       >>> from urlparse import urlparse
+       >>> urlparse('//www.cwi.nl:80/%7Eguido/Python.html')
+       ParseResult(scheme='', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
+                  params='', query='', fragment='')
+       >>> urlparse('www.cwi.nl:80/%7Eguido/Python.html')
+       ParseResult(scheme='', netloc='', path='www.cwi.nl:80/%7Eguido/Python.html',
+                  params='', query='', fragment='')
+       >>> urlparse('help/Python.html')
+       ParseResult(scheme='', netloc='', path='help/Python.html', params='',
+                  query='', fragment='')
+
    If the *default_scheme* argument is specified, it gives the default addressing
    scheme, to be used only if the URL does not specify one.  The default value for
    this argument is the empty string.
 
Index: Lib/urlparse.py
===================================================================
--- Lib/urlparse.py	(revision 64056)
+++ Lib/urlparse.py	(working copy)
@@ -145,7 +144,7 @@
         clear_cache()
     netloc = query = fragment = ''
     i = url.find(':')
-    if i > 0:
+    if i > 0 and not url[i+1].isdigit():
         if url[:i] == 'http': # optimize the common case
             scheme = url[:i].lower()
             url = url[i+1:]