diff --git a/tryton.py b/tryton.py
new file mode 100644
index 0000000000..529fc48a89
--- /dev/null
+++ b/tryton.py
@@ -0,0 +1,3 @@
+#!/usr/bin/env python
+import tryton.tryton
+tryton.tryton.TrytonClient().run()
diff --git a/tryton/gui/window/tree.py b/tryton/gui/window/tree.py
index 8681d9ee0b..0ced552d09 100644
--- a/tryton/gui/window/tree.py
+++ b/tryton/gui/window/tree.py
@@ -271,7 +271,7 @@ class Tree(SignalEvent):
 
     def sc_del(self, widget):
         obj_id = self.tree_sc.sel_id_get()
-        if obj_id != None:
+        if obj_id is not None:
             sc_id = int(self.tree_sc.value_get(2))
             try:
                 rpc.execute('object', 'execute', 'ir.ui.view_sc',
@@ -301,7 +301,7 @@ class Tree(SignalEvent):
 
     def sc_go(self, widget=None, *args):
         obj_id = self.tree_sc.sel_id_get()
-        if obj_id != None:
+        if obj_id is not None:
             self.sig_action(keyword='tree_open', obj_id=obj_id)
 
     def ids_get(self):
diff --git a/tryton/gui/window/view_tree/view_tree.py b/tryton/gui/window/view_tree/view_tree.py
index a1c937d707..a646af03db 100644
--- a/tryton/gui/window/view_tree/view_tree.py
+++ b/tryton/gui/window/view_tree/view_tree.py
@@ -231,11 +231,11 @@ class ViewTreeModel(gtk.GenericTreeModel, gtk.TreeSortable):
 
     def on_iter_children(self, node):
         '''returns the first child of this node'''
-        if node == None:
+        if node is None:
             return [(0, self.tree)]
         node = node[:]
         (i, values) = node[-1]
-        if values[i][2] == None:
+        if values[i][2] is None:
             self._node_expand(values[i])
         if values[i][2] == []:
             return None
@@ -249,22 +249,22 @@ class ViewTreeModel(gtk.GenericTreeModel, gtk.TreeSortable):
 
     def on_iter_n_children(self, node):
         '''returns the number of children of this node'''
-        if node == None:
+        if node is None:
             return len(self.tree)
         (i, values) = node[-1]
-        if values[i][2] == None:
+        if values[i][2] is None:
             self._node_expand(values[i])
         return len(values[i][2])
 
     def on_iter_nth_child(self, node, child):
         '''returns the nth child of this node'''
-        if node == None:
+        if node is None:
             if child < len(self.tree):
                 return [(child, self.tree)]
             return None
         node = node[:]
         (i, values) = node[-1]
-        if values[i][2] == None:
+        if values[i][2] is None:
             self._node_expand(values[i])
         if child < len(values[i][2]):
             node.append((child, values[i][2]))
@@ -273,7 +273,7 @@ class ViewTreeModel(gtk.GenericTreeModel, gtk.TreeSortable):
 
     def on_iter_parent(self, node):
         '''returns the parent of this node'''
-        if node == None:
+        if node is None:
             return None
         return node[:-1]
 
@@ -300,7 +300,7 @@ class ViewTreeModel(gtk.GenericTreeModel, gtk.TreeSortable):
                     if node[0] == val:
                         break
                     path[-1] += 1
-                if (node[2] == None) and (ids != []):
+                if (node[2] is None) and (ids != []):
                     return None
                 tree = node[2]
             return (tuple(path), node)
@@ -379,7 +379,7 @@ class ViewTree(object):
 
     def value_get(self, col):
         sel = self.view.get_selection().get_selected_rows()
-        if sel == None:
+        if sel is None:
             return None
         (model, i) = sel
         if not i:
diff --git a/tryton/gui/window/view_tree/view_tree_sc.py b/tryton/gui/window/view_tree/view_tree_sc.py
index c8e962dd1f..b3e2346380 100644
--- a/tryton/gui/window/view_tree/view_tree_sc.py
+++ b/tryton/gui/window/view_tree/view_tree_sc.py
@@ -46,7 +46,7 @@ class ViewTreeSC(object):
 
     def value_get(self, col):
         sel = self.tree.get_selection().get_selected()
-        if sel == None:
+        if sel is None:
             return None
         (model, i) = sel
         if not i:
@@ -55,6 +55,6 @@ class ViewTreeSC(object):
 
     def sel_id_get(self):
         res = self.value_get(0)
-        if res != None:
+        if res is not None:
             return int(res)
         return None
diff --git a/tryton/gui/window/win_export.py b/tryton/gui/window/win_export.py
index 7d2170e349..8a1e888cb0 100644
--- a/tryton/gui/window/win_export.py
+++ b/tryton/gui/window/win_export.py
@@ -198,7 +198,7 @@ class WinExport(object):
 
     def remove_predef(self, widget):
         sel = self.pref_export.get_selection().get_selected()
-        if sel == None:
+        if sel is None:
             return None
         (model, i) = sel
         if not i:
diff --git a/tryton/pysocket.py b/tryton/pysocket.py
index afbc0151b4..34250ae836 100644
--- a/tryton/pysocket.py
+++ b/tryton/pysocket.py
@@ -1,4 +1,5 @@
 import socket
+# can't use/fall-back pickle due to different interface :-(
 import cPickle
 try:
     import cStringIO as StringIO
@@ -166,6 +167,7 @@ class PySocket:
             msg = msg + chunk
         msgio = StringIO.StringIO(msg)
         unpickler = cPickle.Unpickler(msgio)
+        # cPickle mechanism to import instances (pickle differs here)
         unpickler.find_global = checkfunction
         res = unpickler.load()
         if exception:
diff --git a/tryton/wizard/main.py b/tryton/wizard/main.py
index f4f7238fda..e0151548b9 100644
--- a/tryton/wizard/main.py
+++ b/tryton/wizard/main.py
@@ -118,7 +118,7 @@ class Wizard(object):
                     break
                 (state, new_data) = res2
                 for data in new_data:
-                    if new_data[data] == None:
+                    if new_data[data] is None:
                         del new_data[data]
                 datas['form'].update(new_data)
                 del new_data