diff --git a/openerp/report/pyPdf/utils.py b/openerp/report/pyPdf/utils.py
index 7c1d472d0b7..98eb7a2a2a9 100644
--- a/openerp/report/pyPdf/utils.py
+++ b/openerp/report/pyPdf/utils.py
@@ -78,7 +78,7 @@ class ConvertFunctionsToVirtualList(object):
         len_self = len(self)
         if index < 0:
             # support negative indexes
-            index = len_self + index
+            index += len_self
         if index < 0 or index >= len_self:
             raise IndexError, "sequence index out of range"
         return self.getFunction(index)
diff --git a/openerp/report/render/rml2pdf/trml2pdf.py b/openerp/report/render/rml2pdf/trml2pdf.py
index f9f060db1b9..81faef88a93 100644
--- a/openerp/report/render/rml2pdf/trml2pdf.py
+++ b/openerp/report/render/rml2pdf/trml2pdf.py
@@ -96,7 +96,7 @@ class NumberedCanvas(canvas.Canvas):
         key=self._pageCounter
         if not self.pages.get(key,False):
             while not self.pages.get(key,False):
-                key = key + 1
+                key += 1
         self.setFont("Helvetica", 8)
         self.drawRightString((self._pagesize[0]-30), (self._pagesize[1]-40),
             " %(this)i / %(total)i" % {
@@ -890,7 +890,7 @@ class TinyDocTemplate(platypus.BaseDocTemplate):
         self.canv._storyCount = 0
 
     def ___handle_pageBegin(self):
-        self.page = self.page + 1
+        self.page += 1
         self.pageTemplate.beforeDrawPage(self.canv,self)
         self.pageTemplate.checkPageSize(self.canv,self)
         self.pageTemplate.onPage(self.canv,self)
diff --git a/openerp/tools/amount_to_text.py b/openerp/tools/amount_to_text.py
index 331640a2c28..1dd8f7a6074 100644
--- a/openerp/tools/amount_to_text.py
+++ b/openerp/tools/amount_to_text.py
@@ -57,9 +57,9 @@ def _convert_nnn_fr(val):
     if rem > 0:
         word = to_19_fr[rem] + ' Cent'
         if mod > 0:
-            word = word + ' '
+            word += ' '
     if mod > 0:
-        word = word + _convert_nn_fr(mod)
+        word += _convert_nn_fr(mod)
     return word
 
 def french_number(val):
@@ -125,9 +125,9 @@ def _convert_nnn_nl(val):
     if rem > 0:
         word = to_19_nl[rem] + ' Honderd'
         if mod > 0:
-            word = word + ' '
+            word += ' '
     if mod > 0:
-        word = word + _convert_nn_nl(mod)
+        word += _convert_nn_nl(mod)
     return word
 
 def dutch_number(val):
diff --git a/openerp/tools/amount_to_text_en.py b/openerp/tools/amount_to_text_en.py
index 97d690c70e2..94550588aad 100644
--- a/openerp/tools/amount_to_text_en.py
+++ b/openerp/tools/amount_to_text_en.py
@@ -60,9 +60,9 @@ def _convert_nnn(val):
     if rem > 0:
         word = to_19[rem] + ' Hundred'
         if mod > 0:
-            word = word + ' '
+            word += ' '
     if mod > 0:
-        word = word + _convert_nn(mod)
+        word += _convert_nn(mod)
     return word
 
 def english_number(val):
diff --git a/openerp/tools/graph.py b/openerp/tools/graph.py
index 7c1f00c45d0..785b3b8fee2 100755
--- a/openerp/tools/graph.py
+++ b/openerp/tools/graph.py
@@ -310,7 +310,7 @@ class graph(object):
         """
         if not self.result[node]['y']:
             self.result[node]['y'] = self.order[level]
-            self.order[level] = self.order[level]+1
+            self.order[level] += 1
 
         for sec_end in self.transitions.get(node, []):
             if node!=sec_end:
diff --git a/openerp/tools/misc.py b/openerp/tools/misc.py
index 1b84e3a5eb7..372b048c4d9 100644
--- a/openerp/tools/misc.py
+++ b/openerp/tools/misc.py
@@ -561,8 +561,8 @@ def human_size(sz):
         sz=len(sz)
     s, i = float(sz), 0
     while s >= 1024 and i < len(units)-1:
-        s = s / 1024
-        i = i + 1
+        s /= 1024
+        i += 1
     return "%0.2f %s" % (s, units[i])
 
 def logged(f):