diff --git a/bin/mn b/bin/mn
index a8ae5a8..8dd0d41 100755
--- a/bin/mn
+++ b/bin/mn
@@ -81,19 +81,30 @@ class MininetRunner( object ):
         self.parseArgs()
         self.setup()
         self.begin()
-
-    def parseCustomFile( self, custom ):
-        "Parse custom file and add params before parsing cmd-line options."
-        if os.path.isfile( custom ):
-            execfile( custom, globals(), globals() )
-            if 'topos' in globals(): TOPOS.update( topos )
-            if 'switches' in globals(): SWITCHES.update( switches )
-            if 'hosts' in globals(): HOSTS.update( hosts )
-            if 'controllers' in globals(): CONTROLLERS.update( controllers )
-            if 'validate' in globals(): self.validate = validate
+  
+    def setCustom( self, name, value ):
+        print "got", self, name, value
+        if name in ( 'topos', 'switches', 'hosts', 'controllers' ):
+            # Update dictionaries
+            param = name.upper()
+            globals()[ param ].update( value )
+        elif name == 'validate':
+            # Add custom validate function
+            self.validate = value
         else:
-            raise Exception( 'could not find custom file: %s' % custom )
-
+            # Add or modify global variable or class
+            globals()[ name ] = value
+        
+    def parseCustomFile( self, fileName ):
+        "Parse custom file and add params before parsing cmd-line options."
+        custom = {}
+        if os.path.isfile( fileName ):
+            execfile( fileName, custom, custom )
+            for name in custom:
+                self.setCustom( name, custom[ name ] )
+        else:
+            raise Exception( 'could not find custom file: %s' % fileName )
+        
     def parseArgs( self ):
         """Parse command-line args and return options object.
            returns: opts parse options dict"""
@@ -161,7 +172,7 @@ class MininetRunner( object ):
                              port=self.options.port )
 
         if self.validate:
-            self.validate(self.options)
+            self.validate( self.options )
 
         controllerParams = ControllerParams( 0x0a000000, 8 ) # 10.0.0.0/8
         inNamespace = self.options.inNamespace
diff --git a/custom/custom_example.py b/custom/custom_example.py
index 49e2394..9603533 100644
--- a/custom/custom_example.py
+++ b/custom/custom_example.py
@@ -13,10 +13,10 @@ topology enables one to pass in '--topo=mytopo' from the command line.
 from mininet.topo import Topo, Node
 
 class MyTopo( Topo ):
-    """Simple topology example."""
+    "Simple topology example."
 
     def __init__( self, enable_all = True ):
-        """Create custom topo."""
+        "Create custom topo."
 
         # Add default members to class.
         super( MyTopo, self ).__init__()
@@ -42,4 +42,6 @@ class MyTopo( Topo ):
         self.enable_all()
 
 
-topos = { 'mytopo': ( lambda: MyTopo() ) }
\ No newline at end of file
+topos = { 'mytopo': MyTopo }
+
+# topos = { 'mytopo': ( lambda: MyTopo() ) }
\ No newline at end of file
diff --git a/mininet/cli.py b/mininet/cli.py
index 469f4b1..f28904d 100644
--- a/mininet/cli.py
+++ b/mininet/cli.py
@@ -88,8 +88,7 @@ class CLI( Cmd ):
 
     def do_net( self, args ):
         "List network connections."
-        for switchDpid in self.mn.topo.switches():
-            switch = self.mn.nodes[ switchDpid ]
+        for switch in self.mn.switches:
             info( '%s <->', switch.name )
             for intf in switch.intfs:
                 node = switch.connection[ intf ]
diff --git a/mininet/net.py b/mininet/net.py
index 5666442..4d4dfcb 100755
--- a/mininet/net.py
+++ b/mininet/net.py
@@ -303,14 +303,14 @@ class Mininet( object ):
             ip = topo.ip( hostId )
             host = self.addHost( name, defaultIp=ip, defaultMac=mac )
             self.idToNode[ hostId ] = host
-            info( name )
+            info( name + ' ' )
         info( '\n*** Adding switches:\n' )
         for switchId in sorted( topo.switches() ):
             name = 's' + topo.name( switchId )
             mac = macColonHex( switchId) if self.setMacs else None
             switch = self.addSwitch( name, defaultMac=mac )
             self.idToNode[ switchId ] = switch
-            info( name )
+            info( name + ' ' )
         info( '\n*** Adding edges:\n' )
         for srcId, dstId in sorted( topo.edges() ):
             src, dst = self.idToNode[ srcId ], self.idToNode[ dstId ]