diff -r bb1796870739 Doc/library/urllib.request.rst
--- a/Doc/library/urllib.request.rst	Mon Mar 14 16:38:26 2011 -0400
+++ b/Doc/library/urllib.request.rst	Mon Mar 14 18:01:40 2011 -0400
@@ -204,7 +204,7 @@
    A class to handle HTTP Cookies.
 
 
-.. class:: ProxyHandler(proxies=None)
+.. class:: ProxyHandler(proxies=None, bypass=None)
 
    Cause requests to go through a proxy. If *proxies* is given, it must be a
    dictionary mapping protocol names to URLs of proxies. The default is to read the
@@ -216,6 +216,17 @@
 
    To disable autodetected proxy pass an empty dictionary.
 
+   If *bypass* is given, it must be a list of DNS suffixes separated by
+   commas or '*' for all hosts.  Hostnames matching this list are excluded
+   from proxying.  The default is to read the list of bypass hosts from
+   the environment variable :envvar:`no_proxy`.  If no bypass settings as
+   set, in a Windows environment, proxy bypass settings are obtained from the
+   registry's Internet Settings section and in a Mac OS X environment,
+   proxy bypass information is retrieved from the OS X System
+   Configuration Framework.
+
+   To disable autodetected proxy bypass settings pass an empty list.
+
 
 .. class:: HTTPPasswordMgr()
 
diff -r bb1796870739 Lib/test/test_urllib2_localnet.py
--- a/Lib/test/test_urllib2_localnet.py	Mon Mar 14 16:38:26 2011 -0400
+++ b/Lib/test/test_urllib2_localnet.py	Mon Mar 14 18:01:40 2011 -0400
@@ -17,6 +17,7 @@
 # Self-signed cert file for 'fakehostname'
 CERT_fakehostname = os.path.join(here, 'keycert2.pem')
 
+
 # Loopback http server infrastructure
 
 class LoopbackHttpServer(http.server.HTTPServer):
@@ -249,7 +250,7 @@
         self.server.start()
         self.server.ready.wait()
         proxy_url = "http://127.0.0.1:%d" % self.server.port
-        handler = urllib.request.ProxyHandler({"http" : proxy_url})
+        handler = urllib.request.ProxyHandler({"http" : proxy_url}, bypass=[])
         self.proxy_digest_handler = urllib.request.ProxyDigestAuthHandler()
         self.opener = urllib.request.build_opener(
             handler, self.proxy_digest_handler)
diff -r bb1796870739 Lib/urllib/request.py
--- a/Lib/urllib/request.py	Mon Mar 14 16:38:26 2011 -0400
+++ b/Lib/urllib/request.py	Mon Mar 14 18:01:40 2011 -0400
@@ -661,7 +661,7 @@
     # Proxies must be in front
     handler_order = 100
 
-    def __init__(self, proxies=None):
+    def __init__(self, proxies=None, bypass=None):
         if proxies is None:
             proxies = getproxies()
         assert hasattr(proxies, 'keys'), "proxies must be a mapping"
@@ -670,6 +670,10 @@
             setattr(self, '%s_open' % type,
                     lambda r, proxy=url, type=type, meth=self.proxy_open: \
                     meth(r, proxy, type))
+        if bypass is None:
+            self.bypass_test = proxy_bypass
+        else:
+            self.bypass_test = lambda host: test_proxy_bypass(host, ','.join(bypass))
 
     def proxy_open(self, req, proxy, type):
         orig_type = req.type
@@ -677,7 +681,7 @@
         if proxy_type is None:
             proxy_type = orig_type
 
-        if req.host and proxy_bypass(req.host):
+        if req.host and self.bypass_test(req.host):
             return None
 
         if user and password:
@@ -2188,6 +2192,24 @@
             proxies[name[:-6]] = value
     return proxies
 
+def test_proxy_bypass(host, bypass):
+    """Test if proxies should not be used for a particular host.
+
+    *bypass* argument should be a list of DNS suffixes separated by commas,
+    or '*' for all hosts.
+    """
+    # '*' is special case for always bypass
+    if bypass == '*':
+        return 1
+    # strip port off host
+    hostonly, port = splitport(host)
+    # check if the host ends with any of the DNS suffixes
+    for name in bypass.split(','):
+        if name and (hostonly.endswith(name) or host.endswith(name)):
+            return 1
+    # otherwise, don't bypass
+    return 0
+
 def proxy_bypass_environment(host):
     """Test if proxies should not be used for a particular host.
 
@@ -2195,17 +2217,7 @@
     be a list of DNS suffixes separated by commas, or '*' for all hosts.
     """
     no_proxy = os.environ.get('no_proxy', '') or os.environ.get('NO_PROXY', '')
-    # '*' is special case for always bypass
-    if no_proxy == '*':
-        return 1
-    # strip port off host
-    hostonly, port = splitport(host)
-    # check if the host ends with any of the DNS suffixes
-    for name in no_proxy.split(','):
-        if name and (hostonly.endswith(name) or host.endswith(name)):
-            return 1
-    # otherwise, don't bypass
-    return 0
+    return test_proxy_bypass(no_proxy)
 
 
 # This code tests an OSX specific data structure but is testable on all