diff --git a/sahara/plugins/mapr/versions/version_handler_factory.py b/sahara/plugins/mapr/versions/version_handler_factory.py
index 2e48c384..cc905c13 100644
--- a/sahara/plugins/mapr/versions/version_handler_factory.py
+++ b/sahara/plugins/mapr/versions/version_handler_factory.py
@@ -26,14 +26,13 @@ def _load_versions():
     def mapper(v_dir):
         return m_template % v_dir
 
-    def reducer(versions, m_name):
-        m = __import__(m_name, fromlist=['sahara'])
-        versions[m.version] = getattr(m, 'VersionHandler')()
-        return versions
-
     v_dirs = filter(predicate, os.listdir(d_name))
     m_names = map(mapper, v_dirs)
-    return reduce(reducer, m_names, {})
+    versions = {}
+    for m_name in m_names:
+        m = __import__(m_name, fromlist=['sahara'])
+        versions[m.version] = getattr(m, 'VersionHandler')()
+    return versions
 
 
 class VersionHandlerFactory(object):
diff --git a/sahara/plugins/utils.py b/sahara/plugins/utils.py
index f480f300..4f2a9e83 100644
--- a/sahara/plugins/utils.py
+++ b/sahara/plugins/utils.py
@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import itertools
+
 from oslo_utils import netutils
 from six.moves.urllib import parse as urlparse
 
@@ -32,7 +34,7 @@ def get_instances_count(cluster, node_process=None):
 
 def get_instances(cluster, node_process=None):
     nodes = get_node_groups(cluster, node_process)
-    return reduce(lambda a, b: a + b.instances, nodes, [])
+    return list(itertools.chain(*[node.instances for node in nodes]))
 
 
 def get_instance(cluster, node_process):
diff --git a/sahara/service/validations/base.py b/sahara/service/validations/base.py
index fe67a630..0b59c8d3 100644
--- a/sahara/service/validations/base.py
+++ b/sahara/service/validations/base.py
@@ -14,7 +14,6 @@
 # limitations under the License.
 
 import collections
-import operator
 
 import novaclient.exceptions as nova_ex
 from oslo_config import cfg
@@ -170,9 +169,11 @@ def check_flavor_exists(flavor_id):
 
 def check_security_groups_exist(security_groups):
     security_group_list = nova.client().security_groups.list()
-    allowed_groups = set(reduce(
-        operator.add, [[six.text_type(sg.id), sg.name]
-                       for sg in security_group_list], []))
+    allowed_groups = set()
+    for sg in security_group_list:
+        allowed_groups.add(six.text_type(sg.id))
+        allowed_groups.add(sg.name)
+
     for sg in security_groups:
         if sg not in allowed_groups:
             raise ex.NotFoundException(