remove the mutable default arguments "[]" or "{}"

remove the default arguments "[]" or "{}" when the function is defined.
ref: http://docs.python-guide.org/en/latest/writing/gotchas/

Change-Id: I93de22c6b3a48c3a0e6365756f8b6b5839844826

doc/source/ext/resources.py

@@ -346,7 +346,7 @@ class ContribResourcePages(ResourcePages):
         return 'heat.engine.plugins'
 
 
-def _filter_resources(prefix=None, path=None, statuses=[]):
+def _filter_resources(prefix=None, path=None, statuses=None):
 
     def not_hidden_match(cls):
         return cls.support_status.status != support.HIDDEN
@@ -360,6 +360,7 @@ def _filter_resources(prefix=None, path=None, statuses=[]):
     def status_match(cls):
         return cls.support_status.status in statuses
 
+    statuses = statuses or []
     filtered_resources = {}
     for name in sorted(six.iterkeys(all_resources)):
         if prefix_match(name):

heat/db/sqlalchemy/utils.py

@@ -16,8 +16,8 @@
 import sqlalchemy
 
 
-def clone_table(name, parent, meta, newcols=[], ignorecols=[], swapcols={},
-                ignorecons=[]):
+def clone_table(name, parent, meta, newcols=None, ignorecols=None,
+                swapcols=None, ignorecons=None):
     """Helper function that clones parent table schema onto new table.
 
     :param name: new table name
@@ -30,6 +30,11 @@ def clone_table(name, parent, meta, newcols=[], ignorecols=[], swapcols={},
     :return: sqlalchemy.Table instance
     """
 
+    newcols = newcols or []
+    ignorecols = ignorecols or []
+    swapcols = swapcols or {}
+    ignorecons = ignorecons or []
+
     cols = [c.copy() for c in parent.columns
             if c.name not in ignorecols
             if c.name not in swapcols]

heat/engine/resource.py

@@ -643,7 +643,7 @@ class Resource(object):
         else:
             self.state_set(action, self.COMPLETE)
 
-    def action_handler_task(self, action, args=[], action_prefix=None):
+    def action_handler_task(self, action, args=None, action_prefix=None):
         """A task to call the Resource subclass's handler methods for action.
 
         Calls the handle_<ACTION>() method for the given action and then calls
@@ -655,6 +655,7 @@ class Resource(object):
         If a prefix is supplied, the handler method handle_<PREFIX>_<ACTION>()
         is called instead.
         """
+        args = args or []
         handler_action = action.lower()
         check = getattr(self, 'check_%s_complete' % handler_action, None)
 

heat/tests/test_resource.py

@@ -2900,7 +2900,8 @@ class ResourceHookTest(common.HeatTestCase):
 
 
 class ResourceAvailabilityTest(common.HeatTestCase):
-    def _mock_client_plugin(self, service_types=[], is_available=True):
+    def _mock_client_plugin(self, service_types=None, is_available=True):
+        service_types = service_types or []
         mock_client_plugin = mock.Mock()
         mock_service_types = mock.PropertyMock(return_value=service_types)
         type(mock_client_plugin).service_types = mock_service_types

heat/tests/test_template.py

@@ -89,7 +89,8 @@ class DummyClass(object):
 
 
 class TemplatePluginFixture(fixtures.Fixture):
-    def __init__(self, templates={}):
+    def __init__(self, templates=None):
+        templates = templates or {}
         super(TemplatePluginFixture, self).__init__()
         self.templates = [extension.Extension(k, None, v, None)
                           for (k, v) in templates.items()]