diff --git a/bindings/python/ns3modulegen.py b/bindings/python/ns3modulegen.py
index ea266248d..680c8a213 100755
--- a/bindings/python/ns3modulegen.py
+++ b/bindings/python/ns3modulegen.py
@@ -81,7 +81,7 @@ class MyMultiSectionFactory(MultiSectionFactory):
     def close(self):
         self.header_sink.file.close()
         self.main_sink.file.close()
-        for sink in self.section_sinks.itervalues():
+        for sink in self.section_sinks.values():
             sink.file.close()
 
 
diff --git a/src/visualizer/model/visual-simulator-impl.cc b/src/visualizer/model/visual-simulator-impl.cc
index 58225a5b3..d298540d8 100644
--- a/src/visualizer/model/visual-simulator-impl.cc
+++ b/src/visualizer/model/visual-simulator-impl.cc
@@ -112,11 +112,17 @@ VisualSimulatorImpl::IsFinished (void) const
 void
 VisualSimulatorImpl::Run (void)
 {
-  if (!Py_IsInitialized ()) 
+  if (!Py_IsInitialized ())
     {
-      const char *argv[] = { "python", NULL};
-      Py_Initialize ();
-      PySys_SetArgv (1, (char**) argv);
+      #if PY_MAJOR_VERSION >= 3
+        const wchar_t *argv[] = { L"python", NULL};
+        Py_Initialize ();
+        PySys_SetArgv (1, (wchar_t**) argv);
+      #else
+        const char *argv[] = { "python", NULL};
+        Py_Initialize ();
+        PySys_SetArgv (1, (char**) argv);
+      #endif
       PyRun_SimpleString (
                           "import visualizer\n"
                           "visualizer.start();\n"
diff --git a/src/visualizer/visualizer/__init__.py b/src/visualizer/visualizer/__init__.py
index 10a4dbd41..1a4d80f89 100644
--- a/src/visualizer/visualizer/__init__.py
+++ b/src/visualizer/visualizer/__init__.py
@@ -1,3 +1,3 @@
 
-from core import start, register_plugin, set_bounds, add_initialization_hook
+from .core import start, register_plugin, set_bounds, add_initialization_hook
 
diff --git a/src/visualizer/visualizer/base.py b/src/visualizer/visualizer/base.py
index 17668b833..5ef666974 100644
--- a/src/visualizer/visualizer/base.py
+++ b/src/visualizer/visualizer/base.py
@@ -1,3 +1,4 @@
+from __future__ import print_function
 import ns.point_to_point
 import ns.csma
 import ns.wifi
@@ -5,7 +6,6 @@ import ns.bridge
 import ns.internet
 import ns.mesh
 import ns.wimax
-import ns.wimax
 import ns.lte
 
 from gi.repository import GObject
@@ -126,15 +126,15 @@ def load_plugins():
             continue
         try:
             plugin_module = __import__(name)
-        except ImportError, ex:
-            print >> sys.stderr, "Could not load plugin %r: %s" % (filename, str(ex))
+        except ImportError as ex:
+            print("Could not load plugin %r: %s" % (filename, str(ex)), file=sys.stderr)
             continue
         try:
             plugin_func = plugin_module.register
         except AttributeError:
-            print >> sys.stderr, "Plugin %r has no 'register' function" % name
+            print("Plugin %r has no 'register' function" % name, file=sys.stderr)
         else:
-            #print >> sys.stderr, "Plugin %r registered" % name
+            #print("Plugin %r registered" % name, file=sys.stderr)
             register_plugin(plugin_func, name, plugin_module)
     sys.path = old_path
 
diff --git a/src/visualizer/visualizer/core.py b/src/visualizer/visualizer/core.py
index 1e69de33c..75720241c 100644
--- a/src/visualizer/visualizer/core.py
+++ b/src/visualizer/visualizer/core.py
@@ -31,6 +31,9 @@ import math
 import os
 import sys
 
+if sys.version_info > (3,):
+    long = int
+
 try:
     import gi
     gi.require_version('GooCanvas', '2.0')
@@ -45,13 +48,14 @@ try:
     from gi.repository import Pango
     from gi.repository import GooCanvas
     import threading
-    import hud
+    from . import hud
     #import time
     try:
         import svgitem
     except ImportError:
         svgitem = None
-except ImportError as _import_error:
+except ImportError as e:
+    _import_error = e
     import dummy_threading as threading
 else:
     _import_error = None
@@ -61,10 +65,10 @@ try:
 except ImportError:
     ipython_view = None
 
-from base import InformationWindow, PyVizObject, Link, lookup_netdevice_traits, PIXELS_PER_METER
-from base import transform_distance_simulation_to_canvas, transform_point_simulation_to_canvas
-from base import transform_distance_canvas_to_simulation, transform_point_canvas_to_simulation
-from base import load_plugins, register_plugin, plugins
+from .base import InformationWindow, PyVizObject, Link, lookup_netdevice_traits, PIXELS_PER_METER
+from .base import transform_distance_simulation_to_canvas, transform_point_simulation_to_canvas
+from .base import transform_distance_canvas_to_simulation, transform_point_canvas_to_simulation
+from .base import load_plugins, register_plugin, plugins
 
 PI_OVER_2 = math.pi/2
 PI_TIMES_2 = math.pi*2
@@ -773,7 +777,7 @@ class Visualizer(GObject.GObject):
         assert isinstance(mode, ShowTransmissionsMode)
         self._show_transmissions_mode = mode
         if self._show_transmissions_mode == ShowTransmissionsMode.ALL:
-            self.simulation.set_nodes_of_interest(range(ns.network.NodeList.GetNNodes()))
+            self.simulation.set_nodes_of_interest(list(range(ns.network.NodeList.GetNNodes())))
         elif self._show_transmissions_mode == ShowTransmissionsMode.NONE:
             self.simulation.set_nodes_of_interest([])
         elif self._show_transmissions_mode == ShowTransmissionsMode.SELECTED:
@@ -854,7 +858,7 @@ class Visualizer(GObject.GObject):
         settings_hbox.pack_start(vbox, False, False, 6)
         self.node_size_adjustment = scale.get_adjustment()
         def node_size_changed(adj):
-            for node in self.nodes.itervalues():
+            for node in self.nodes.values():
                 node.set_size(adj.get_value())
         self.node_size_adjustment.connect("value-changed", node_size_changed)
         self.node_size_adjustment.set_lower(0.01)
@@ -1218,7 +1222,7 @@ class Visualizer(GObject.GObject):
         self.emit("update-view")
 
     def _update_node_positions(self):
-        for node in self.nodes.itervalues():
+        for node in self.nodes.values():
             if node.has_mobility:
                 ns3_node = ns.network.NodeList.GetNode(node.node_index)
                 mobility = ns3_node.GetObject(ns.mobility.MobilityModel.GetTypeId())
@@ -1300,7 +1304,7 @@ class Visualizer(GObject.GObject):
 
         k = self.node_size_adjustment.get_value()/5
 
-        for (transmitter_id, receiver_id), (rx_bytes, rx_count) in transmissions_average.iteritems():
+        for (transmitter_id, receiver_id), (rx_bytes, rx_count) in transmissions_average.items():
             transmitter = self.get_node(transmitter_id)
             receiver = self.get_node(receiver_id)
             try:
@@ -1381,7 +1385,7 @@ class Visualizer(GObject.GObject):
 
         k = self.node_size_adjustment.get_value()/5
 
-        for transmitter_id, (drop_bytes, drop_count) in drops_average.iteritems():
+        for transmitter_id, (drop_bytes, drop_count) in drops_average.items():
             transmitter = self.get_node(transmitter_id)
             try:
                 arrow, label = old_arrows.pop()
@@ -1497,7 +1501,7 @@ class Visualizer(GObject.GObject):
         if not self.nodes:
             return
         self._update_node_positions()
-        positions = [node.get_position() for node in self.nodes.itervalues()]
+        positions = [node.get_position() for node in self.nodes.values()]
         min_x, min_y = min(x for (x,y) in positions), min(y for (x,y) in positions)
         max_x, max_y = max(x for (x,y) in positions), max(y for (x,y) in positions)
         min_x_px, min_y_px = self.canvas.convert_to_pixels(min_x, min_y)
diff --git a/src/visualizer/visualizer/hud.py b/src/visualizer/visualizer/hud.py
index 89fa66be8..ff7c2d5a3 100644
--- a/src/visualizer/visualizer/hud.py
+++ b/src/visualizer/visualizer/hud.py
@@ -1,5 +1,5 @@
-import core
 import math
+from . import core
 from gi.repository import Pango
 from gi.repository import Gtk
 from gi.repository import GooCanvas
diff --git a/src/visualizer/visualizer/ipython_view.py b/src/visualizer/visualizer/ipython_view.py
index ee547668f..34f9db7a9 100644
--- a/src/visualizer/visualizer/ipython_view.py
+++ b/src/visualizer/visualizer/ipython_view.py
@@ -319,11 +319,11 @@ class IterableIPShell:
     @return none
     """
     stat = 0
-    if verbose or debug: print header+cmd
+    if verbose or debug: print(header+cmd)
     # flush stdout so we don't mangle python's buffering
     if not debug:
       input, output = os.popen4(cmd)
-      print output.read()
+      print(output.read())
       output.close()
       input.close()
 
diff --git a/src/visualizer/visualizer/plugins/olsr.py b/src/visualizer/visualizer/plugins/olsr.py
index eb59e5e2d..726b11610 100644
--- a/src/visualizer/visualizer/plugins/olsr.py
+++ b/src/visualizer/visualizer/plugins/olsr.py
@@ -120,7 +120,7 @@ def populate_node_menu(viz, node, menu):
     ns3_node = ns.network.NodeList.GetNode(node.node_index)
     olsr = ns3_node.GetObject(ns.olsr.olsr.RoutingProtocol.GetTypeId())
     if olsr is None:
-        print "No OLSR"
+        print("No OLSR")
         return
 
     menu_item = Gtk.MenuItem("Show OLSR Routing Table")
diff --git a/src/visualizer/visualizer/plugins/wifi_intrastructure_link.py b/src/visualizer/visualizer/plugins/wifi_intrastructure_link.py
index 8cd9a8ffa..7005856bf 100644
--- a/src/visualizer/visualizer/plugins/wifi_intrastructure_link.py
+++ b/src/visualizer/visualizer/plugins/wifi_intrastructure_link.py
@@ -131,7 +131,7 @@ class WifiLinkMonitor(object):
         self.access_points = {}
         self.stations = []
 
-        for node in viz.nodes.itervalues():
+        for node in viz.nodes.values():
             ns3_node = ns.network.NodeList.GetNode(node.node_index)
             for devI in range(ns3_node.GetNDevices()):
                 dev = ns3_node.GetDevice(devI)
diff --git a/src/visualizer/visualizer/svgitem.py b/src/visualizer/visualizer/svgitem.py
index 261803d91..c281110d6 100644
--- a/src/visualizer/visualizer/svgitem.py
+++ b/src/visualizer/visualizer/svgitem.py
@@ -120,7 +120,7 @@ class SvgItem(GooCanvas.ItemSimple):
             self.changed(True)
 
         else:
-            raise AttributeError, 'unknown property %s' % pspec.name
+            raise AttributeError('unknown property %s' % pspec.name)
 
     def _size_changed(self):
         """!
@@ -172,7 +172,7 @@ class SvgItem(GooCanvas.ItemSimple):
             return self.height
 
         else:
-            raise AttributeError, 'unknown property %s' % pspec.name
+            raise AttributeError('unknown property %s' % pspec.name)
 
     def do_simple_paint(self, cr, bounds):
         """!