diff --git a/openerp/addons/base/ir/ir_default.py b/openerp/addons/base/ir/ir_default.py
index d229ee4cb5c..a51405b32c1 100644
--- a/openerp/addons/base/ir/ir_default.py
+++ b/openerp/addons/base/ir/ir_default.py
@@ -34,7 +34,7 @@ class ir_default(osv.osv):
         'company_id': fields.many2one('res.company','Company')
     }
 
-    def _get_company_id(self, cr, uid, context={}):
+    def _get_company_id(self, cr, uid, context=None):
         res = self.pool.get('res.users').read(cr, uid, [uid], ['company_id'], context=context)
         if res and res[0]['company_id']:
             return res[0]['company_id'][0]
diff --git a/openerp/addons/base/ir/ir_filters.py b/openerp/addons/base/ir/ir_filters.py
index e18d3346db6..8a6fc587580 100644
--- a/openerp/addons/base/ir/ir_filters.py
+++ b/openerp/addons/base/ir/ir_filters.py
@@ -53,7 +53,7 @@ class ir_filters(osv.osv):
             return False
         return self.create(cr, uid, vals, context)
 
-    def _auto_init(self, cr, context={}):
+    def _auto_init(self, cr, context=None):
         super(ir_filters, self)._auto_init(cr, context)
         # Use unique index to implement unique constraint on the lowercase name (not possible using a constraint)
         cr.execute("SELECT indexname FROM pg_indexes WHERE indexname = 'ir_filters_name_model_uid_unique_index'")
diff --git a/openerp/addons/base/ir/ir_model.py b/openerp/addons/base/ir/ir_model.py
index 014d5652891..7c149a618a2 100644
--- a/openerp/addons/base/ir/ir_model.py
+++ b/openerp/addons/base/ir/ir_model.py
@@ -161,7 +161,7 @@ class ir_model(osv.osv):
             #pooler.restart_pool(cr.dbname)
         return res
 
-    def instanciate(self, cr, user, model, context={}):
+    def instanciate(self, cr, user, model, context=None):
         class x_custom_model(osv.osv):
             pass
         x_custom_model._name = model
diff --git a/openerp/addons/base/ir/ir_sequence.py b/openerp/addons/base/ir/ir_sequence.py
index c2f71910231..a0a260131ea 100644
--- a/openerp/addons/base/ir/ir_sequence.py
+++ b/openerp/addons/base/ir/ir_sequence.py
@@ -38,7 +38,7 @@ class ir_sequence_type(openerp.osv.osv.osv):
         ('code_unique', 'unique(code)', '`code` must be unique.'),
     ]
 
-def _code_get(self, cr, uid, context={}):
+def _code_get(self, cr, uid, context=None):
     cr.execute('select code, name from ir_sequence_type')
     return cr.fetchall()
 
diff --git a/openerp/addons/base/ir/ir_translation.py b/openerp/addons/base/ir/ir_translation.py
index 44f5d24823d..d8127da0593 100644
--- a/openerp/addons/base/ir/ir_translation.py
+++ b/openerp/addons/base/ir/ir_translation.py
@@ -62,7 +62,7 @@ class ir_translation(osv.osv):
         'xml_id': fields.char('External ID', size=128, help='Maps to the ir_model_data for which this translation is provided.'),
     }
 
-    def _auto_init(self, cr, context={}):
+    def _auto_init(self, cr, context=None):
         super(ir_translation, self)._auto_init(cr, context)
 
         # FIXME: there is a size limit on btree indexed values so we can't index src column with normal btree. 
diff --git a/openerp/addons/base/ir/ir_ui_view.py b/openerp/addons/base/ir/ir_ui_view.py
index c44ff716519..a4648a001be 100644
--- a/openerp/addons/base/ir/ir_ui_view.py
+++ b/openerp/addons/base/ir/ir_ui_view.py
@@ -109,7 +109,7 @@ class view(osv.osv):
                       (view_id, model))
         return cr.fetchall()
 
-    def write(self, cr, uid, ids, vals, context={}):
+    def write(self, cr, uid, ids, vals, context=None):
         if not isinstance(ids, (list, tuple)):
             ids = [ids]
         result = super(view, self).write(cr, uid, ids, vals, context)
@@ -122,7 +122,7 @@ class view(osv.osv):
 
         return result
 
-    def graph_get(self, cr, uid, id, model, node_obj, conn_obj, src_node, des_node,label,scale,context={}):
+    def graph_get(self, cr, uid, id, model, node_obj, conn_obj, src_node, des_node, label, scale, context=None):
         if not label:
             label = []
         nodes=[]
diff --git a/openerp/addons/base/ir/workflow/print_instance.py b/openerp/addons/base/ir/workflow/print_instance.py
index 747ae5622fe..7ca9426d1d4 100644
--- a/openerp/addons/base/ir/workflow/print_instance.py
+++ b/openerp/addons/base/ir/workflow/print_instance.py
@@ -210,7 +210,7 @@ class report_graph(report.interface.report_int):
         else:
             return (False, False, False)
 
-    def create(self, cr, uid, ids, data, context={}):
+    def create(self, cr, uid, ids, data, context=None):
         self.obj = report_graph_instance(cr, uid, ids, data)
         return (self.obj.get(), 'pdf')
 
diff --git a/openerp/addons/base/ir/workflow/workflow.py b/openerp/addons/base/ir/workflow/workflow.py
index c638855aacf..edd070ae50d 100644
--- a/openerp/addons/base/ir/workflow/workflow.py
+++ b/openerp/addons/base/ir/workflow/workflow.py
@@ -45,7 +45,7 @@ class workflow(osv.osv):
         wf_service.clear_cache(cr, user)
         return super(workflow, self).write(cr, user, ids, vals, context=context)
 
-    def get_active_workitems(self, cr, uid, res, res_id, context={}):
+    def get_active_workitems(self, cr, uid, res, res_id, context=None):
         
         cr.execute('select * from wkf where osv=%s limit 1',(res,))
         wkfinfo = cr.dictfetchone()
@@ -212,7 +212,7 @@ class wkf_triggers(osv.osv):
         'instance_id': fields.many2one('workflow.instance', 'Destination Instance', ondelete="cascade"),
         'workitem_id': fields.many2one('workflow.workitem', 'Workitem', required=True, ondelete="cascade"),
     }
-    def _auto_init(self, cr, context={}):
+    def _auto_init(self, cr, context=None):
         super(wkf_triggers, self)._auto_init(cr, context)
         cr.execute('SELECT indexname FROM pg_indexes WHERE indexname = \'wkf_triggers_res_id_model_index\'')
         if not cr.fetchone():
diff --git a/openerp/addons/base/module/module.py b/openerp/addons/base/module/module.py
index b7f9995e2c9..3a6a044832f 100644
--- a/openerp/addons/base/module/module.py
+++ b/openerp/addons/base/module/module.py
@@ -402,7 +402,7 @@ class module(osv.osv):
         }
 
     # update the list of available packages
-    def update_list(self, cr, uid, context={}):
+    def update_list(self, cr, uid, context=None):
         res = [0, 0] # [update, add]
 
         known_mods = self.browse(cr, uid, self.search(cr, uid, []))
diff --git a/openerp/addons/base/res/ir_property.py b/openerp/addons/base/res/ir_property.py
index 43451f824a1..496bfffe1a2 100644
--- a/openerp/addons/base/res/ir_property.py
+++ b/openerp/addons/base/res/ir_property.py
@@ -156,7 +156,7 @@ class ir_property(osv.osv):
             return time.strftime('%Y-%m-%d', time.strptime(record.value_datetime, '%Y-%m-%d %H:%M:%S'))
         return False
 
-    def get(self, cr, uid, name, model, res_id=False, context={}):
+    def get(self, cr, uid, name, model, res_id=False, context=None):
         domain = self._get_domain(cr, uid, name, model, context=context)
         if domain is not None:
             domain = [('res_id', '=', res_id)] + domain
diff --git a/openerp/addons/base/res/res_bank.py b/openerp/addons/base/res/res_bank.py
index ce1cd1c6a24..9184cf2ad1c 100644
--- a/openerp/addons/base/res/res_bank.py
+++ b/openerp/addons/base/res/res_bank.py
@@ -190,7 +190,7 @@ class res_partner_bank(osv.osv):
             res.append((val.id, result))
         return res
 
-    def onchange_company_id(self, cr, uid, ids, company_id, context={}):
+    def onchange_company_id(self, cr, uid, ids, company_id, context=None):
         result = {}
         if company_id:
             c = self.pool.get('res.company').browse(cr, uid, company_id, context=context)
@@ -201,7 +201,7 @@ class res_partner_bank(osv.osv):
                 result = r
         return result
 
-    def onchange_bank_id(self, cr, uid, ids, bank_id, context={}):
+    def onchange_bank_id(self, cr, uid, ids, bank_id, context=None):
         result = {}
         if bank_id:
             bank = self.pool.get('res.bank').browse(cr, uid, bank_id, context=context)
@@ -210,7 +210,7 @@ class res_partner_bank(osv.osv):
         return {'value': result}
 
 
-    def onchange_partner_id(self, cr, uid, id, partner_id, context={}):
+    def onchange_partner_id(self, cr, uid, id, partner_id, context=None):
         result = {}
         if partner_id:
             part = self.pool.get('res.partner').browse(cr, uid, partner_id, context=context)
diff --git a/openerp/addons/base/res/res_company.py b/openerp/addons/base/res/res_company.py
index e2c5e091f97..7a6b7007833 100644
--- a/openerp/addons/base/res/res_company.py
+++ b/openerp/addons/base/res/res_company.py
@@ -148,7 +148,7 @@ class res_company(osv.osv):
     _sql_constraints = [
         ('name_uniq', 'unique (name)', 'The company name must be unique !')
     ]
-    def on_change_header(self, cr, uid, ids, phone, email, fax, website, vat, reg=False, context={}):
+    def on_change_header(self, cr, uid, ids, phone, email, fax, website, vat, reg=False, context=None):
         val = []
         if phone: val.append(_('Phone: ')+phone)
         if fax: val.append(_('Fax: ')+fax)
@@ -201,7 +201,7 @@ class res_company(osv.osv):
         ids =  self.search(cr, uid, [('parent_id','child_of',[company])])
         return ids
 
-    def _get_partner_hierarchy(self, cr, uid, company_id, context={}):
+    def _get_partner_hierarchy(self, cr, uid, company_id, context=None):
         if company_id:
             parent_id = self.browse(cr, uid, company_id)['parent_id']
             if parent_id:
@@ -210,7 +210,7 @@ class res_company(osv.osv):
                 return self._get_partner_descendance(cr, uid, company_id, [], context)
         return []
 
-    def _get_partner_descendance(self, cr, uid, company_id, descendance, context={}):
+    def _get_partner_descendance(self, cr, uid, company_id, descendance, context=None):
         descendance.append(self.browse(cr, uid, company_id).partner_id.id)
         for child_id in self._get_company_children(cr, uid, company_id):
             if child_id != company_id:
@@ -239,7 +239,7 @@ class res_company(osv.osv):
         self.cache_restart(cr)
         return super(res_company, self).write(cr, *args, **argv)
 
-    def _get_euro(self, cr, uid, context={}):
+    def _get_euro(self, cr, uid, context=None):
         try:
             return self.pool.get('res.currency').search(cr, uid, [])[0]
         except:
diff --git a/openerp/addons/base/res/res_lang.py b/openerp/addons/base/res/res_lang.py
index 50841241f8a..246163536ea 100644
--- a/openerp/addons/base/res/res_lang.py
+++ b/openerp/addons/base/res/res_lang.py
@@ -125,10 +125,10 @@ class lang(osv.osv):
                     return False
         return True
 
-    def _get_default_date_format(self,cursor,user,context={}):
+    def _get_default_date_format(self, cursor, user, context=None):
         return '%m/%d/%Y'
 
-    def _get_default_time_format(self,cursor,user,context={}):
+    def _get_default_time_format(self, cursor, user, context=None):
         return '%H:%M:%S'
 
     _columns = {
diff --git a/openerp/addons/base/res/res_log.py b/openerp/addons/base/res/res_log.py
index 26e1eaeed69..0ec39dbf615 100644
--- a/openerp/addons/base/res/res_log.py
+++ b/openerp/addons/base/res/res_log.py
@@ -41,7 +41,7 @@ class res_log(osv.osv):
     _order='create_date desc'
 
     _index_name = 'res_log_uid_read'
-    def _auto_init(self, cr, context={}):
+    def _auto_init(self, cr, context=None):
         super(res_log, self)._auto_init(cr, context)
         cr.execute('SELECT 1 FROM pg_indexes WHERE indexname=%s',
                    (self._index_name,))
diff --git a/openerp/addons/base/res/res_partner.py b/openerp/addons/base/res/res_partner.py
index b250269cb0e..6b8d2a41c50 100644
--- a/openerp/addons/base/res/res_partner.py
+++ b/openerp/addons/base/res/res_partner.py
@@ -98,7 +98,7 @@ class res_partner_title(osv.osv):
     _order = 'name'
 res_partner_title()
 
-def _lang_get(self, cr, uid, context={}):
+def _lang_get(self, cr, uid, context=None):
     obj = self.pool.get('res.lang')
     ids = obj.search(cr, uid, [], context=context)
     res = obj.read(cr, uid, ids, ['code', 'name'], context)
@@ -142,7 +142,9 @@ class res_partner(osv.osv):
         'color': fields.integer('Color Index'),
     }
 
-    def _default_category(self, cr, uid, context={}):
+    def _default_category(self, cr, uid, context=None):
+        if context is None:
+            context = {}
         if 'category_id' in context and context['category_id']:
             return [context['category_id']]
         return []
@@ -156,7 +158,9 @@ class res_partner(osv.osv):
         'color': 0,
     }
 
-    def copy(self, cr, uid, id, default={}, context={}):
+    def copy(self, cr, uid, id, default=None, context=None):
+        if default is None:
+            default = {}
         name = self.read(cr, uid, [id], ['name'])[0]['name']
         default.update({'name': name+ _(' (copy)'), 'events':[]})
         return super(res_partner, self).copy(cr, uid, id, default, context)
@@ -182,10 +186,12 @@ class res_partner(osv.osv):
 
 #   _constraints = [(_check_ean_key, 'Error: Invalid ean code', ['ean13'])]
 
-    def name_get(self, cr, uid, ids, context={}):
+    def name_get(self, cr, uid, ids, context=None):
+        if context is None:
+            context = {}
         if not len(ids):
             return []
-        if context and context.get('show_ref'):
+        if context.get('show_ref', False):
             rec_name = 'ref'
         else:
             rec_name = 'name'
@@ -224,7 +230,9 @@ class res_partner(osv.osv):
             ids = ids[16:]
         return True
 
-    def address_get(self, cr, uid, ids, adr_pref=['default']):
+    def address_get(self, cr, uid, ids, adr_pref=None):
+        if adr_pref is None:
+            adr_pref = ['default']
         address_obj = self.pool.get('res.partner.address')
         address_ids = address_obj.search(cr, uid, [('partner_id', 'in', ids)])
         address_rec = address_obj.read(cr, uid, address_ids, ['type'])
@@ -308,7 +316,7 @@ class res_partner_address(osv.osv):
         'company_id': lambda s,cr,uid,c: s.pool.get('res.company')._company_default_get(cr, uid, 'res.partner.address', context=c),
     }
 
-    def name_get(self, cr, user, ids, context={}):
+    def name_get(self, cr, user, ids, context=None):
         if context is None:
             context = {}
         if not len(ids):
diff --git a/openerp/addons/base/res/res_request.py b/openerp/addons/base/res/res_request.py
index d7c87274ea1..e5afd1c8387 100644
--- a/openerp/addons/base/res/res_request.py
+++ b/openerp/addons/base/res/res_request.py
@@ -22,7 +22,7 @@
 from osv import osv, fields
 import time
 
-def _links_get(self, cr, uid, context={}):
+def _links_get(self, cr, uid, context=None):
     obj = self.pool.get('res.request.link')
     ids = obj.search(cr, uid, [])
     res = obj.read(cr, uid, ids, ['object', 'name'], context)