diff --git a/ryu/lib/addrconv.py b/ryu/lib/addrconv.py
index 36a00fa2..bf069e04 100644
--- a/ryu/lib/addrconv.py
+++ b/ryu/lib/addrconv.py
@@ -40,6 +40,7 @@ class AddressConverter(object):
         return str(self._addr(self._strat.packed_to_int(bin),
                               **self._addr_kwargs))
 
+
 ipv4 = AddressConverter(netaddr.IPAddress, netaddr.strategy.ipv4,
                         fallback=netaddr.IPNetwork, version=4)
 ipv6 = AddressConverter(netaddr.IPAddress, netaddr.strategy.ipv6,
@@ -48,5 +49,7 @@ ipv6 = AddressConverter(netaddr.IPAddress, netaddr.strategy.ipv6,
 
 class mac_mydialect(netaddr.mac_unix):
     word_fmt = '%.2x'
+
+
 mac = AddressConverter(netaddr.EUI, netaddr.strategy.eui48, version=48,
                        dialect=mac_mydialect)
diff --git a/ryu/lib/mrtlib.py b/ryu/lib/mrtlib.py
index b6d76983..83b4e536 100644
--- a/ryu/lib/mrtlib.py
+++ b/ryu/lib/mrtlib.py
@@ -236,6 +236,7 @@ class UnknownMrtMessage(MrtMessage):
     def serialize(self):
         return self.buf
 
+
 # Registers self to unknown(default) type
 UnknownMrtMessage._UNKNOWN_TYPE = UnknownMrtMessage
 
@@ -298,6 +299,7 @@ class Ospf2MrtRecord(MrtCommonRecord):
             message=message, timestamp=timestamp, type_=type_,
             subtype=subtype, length=length)
 
+
 # Registers self to unknown(default) type
 Ospf2MrtMessage._UNKNOWN_TYPE = Ospf2MrtMessage
 
diff --git a/ryu/lib/packet/bgp.py b/ryu/lib/packet/bgp.py
index ccea4963..9e501515 100644
--- a/ryu/lib/packet/bgp.py
+++ b/ryu/lib/packet/bgp.py
@@ -565,6 +565,7 @@ class RouteFamily(StringifyMixin):
     def __hash__(self):
         return hash((self.afi, self.safi))
 
+
 # Route Family Singleton
 RF_IPv4_UC = RouteFamily(addr_family.IP, subaddr_family.UNICAST)
 RF_IPv6_UC = RouteFamily(addr_family.IP6, subaddr_family.UNICAST)
diff --git a/ryu/lib/packet/ipv4.py b/ryu/lib/packet/ipv4.py
index 2547f06a..83990719 100644
--- a/ryu/lib/packet/ipv4.py
+++ b/ryu/lib/packet/ipv4.py
@@ -142,6 +142,7 @@ class ipv4(packet_base.PacketBase):
         struct.pack_into('!H', hdr, 10, self.csum)
         return hdr
 
+
 ipv4.register_packet_type(icmp.icmp, inet.IPPROTO_ICMP)
 ipv4.register_packet_type(igmp.igmp, inet.IPPROTO_IGMP)
 ipv4.register_packet_type(tcp.tcp, inet.IPPROTO_TCP)
diff --git a/ryu/lib/packet/ipv6.py b/ryu/lib/packet/ipv6.py
index 3ab3aacf..524a0864 100644
--- a/ryu/lib/packet/ipv6.py
+++ b/ryu/lib/packet/ipv6.py
@@ -143,6 +143,7 @@ class ipv6(packet_base.PacketBase):
             ext_hdrs_len += len(ext_hdr)
         return self._MIN_LEN + ext_hdrs_len
 
+
 ipv6.register_packet_type(icmpv6.icmpv6, inet.IPPROTO_ICMPV6)
 ipv6.register_packet_type(tcp.tcp, inet.IPPROTO_TCP)
 ipv6.register_packet_type(udp.udp, inet.IPPROTO_UDP)
diff --git a/ryu/lib/packet/ospf.py b/ryu/lib/packet/ospf.py
index 398dd9c0..5c156c03 100644
--- a/ryu/lib/packet/ospf.py
+++ b/ryu/lib/packet/ospf.py
@@ -695,6 +695,7 @@ class OSPFMessage(packet_base.PacketBase, type_desc.TypeDisp):
         struct.pack_into("!H", buf, 12, csum)
         return buf
 
+
 # alias
 ospf = OSPFMessage
 
diff --git a/ryu/lib/packet/packet.py b/ryu/lib/packet/packet.py
index 7de24c18..2db641b7 100644
--- a/ryu/lib/packet/packet.py
+++ b/ryu/lib/packet/packet.py
@@ -185,5 +185,6 @@ def _PacketBase__div__(self, trailer):
     pkt.add_protocol(trailer)
     return pkt
 
+
 packet_base.PacketBase.__div__ = _PacketBase__div__
 packet_base.PacketBase.__truediv__ = _PacketBase__div__
diff --git a/ryu/lib/packet/packet_utils.py b/ryu/lib/packet/packet_utils.py
index 546b49cf..30259e31 100644
--- a/ryu/lib/packet/packet_utils.py
+++ b/ryu/lib/packet/packet_utils.py
@@ -99,6 +99,7 @@ def checksum_ip(ipvx, length, payload):
     buf = header + payload
     return checksum(buf)
 
+
 _MODX = 4102
 
 
diff --git a/ryu/lib/type_desc.py b/ryu/lib/type_desc.py
index 3e4061a5..415fb574 100644
--- a/ryu/lib/type_desc.py
+++ b/ryu/lib/type_desc.py
@@ -44,6 +44,7 @@ class IntDescr(TypeDescr):
             i //= 256
         return binary
 
+
 Int1 = IntDescr(1)
 Int2 = IntDescr(2)
 Int3 = IntDescr(3)
@@ -91,6 +92,7 @@ class IntDescrMlt(TypeDescr):
             binary += b
         return binary
 
+
 Int4Double = IntDescrMlt(4, 2)
 
 
diff --git a/ryu/ofproto/nicira_ext.py b/ryu/ofproto/nicira_ext.py
index 416c6256..9e0f8873 100644
--- a/ryu/ofproto/nicira_ext.py
+++ b/ryu/ofproto/nicira_ext.py
@@ -428,6 +428,7 @@ def nxm_nx_reg(idx):
 def nxm_nx_reg_w(idx):
     return nxm_header_w(0x0001, idx, 4)
 
+
 NXM_HEADER_PACK_STRING = '!I'
 
 #
diff --git a/ryu/ofproto/ofproto_v1_0_parser.py b/ryu/ofproto/ofproto_v1_0_parser.py
index 4da5a072..c2a25988 100644
--- a/ryu/ofproto/ofproto_v1_0_parser.py
+++ b/ryu/ofproto/ofproto_v1_0_parser.py
@@ -822,6 +822,7 @@ class OFPActionVendor(OFPAction):
         msg_pack_into(ofproto.OFP_ACTION_VENDOR_HEADER_PACK_STR,
                       buf, offset, self.type, self.len, self.vendor)
 
+
 # OpenFlow1.2 or later compatible
 OFPActionExperimenter = OFPActionVendor
 
diff --git a/ryu/ofproto/ofproto_v1_2.py b/ryu/ofproto/ofproto_v1_2.py
index 9c8aa906..1c8a971d 100644
--- a/ryu/ofproto/ofproto_v1_2.py
+++ b/ryu/ofproto/ofproto_v1_2.py
@@ -792,6 +792,7 @@ def oxm_tlv_header_extract_length(header):
         length = header & 0xff
     return length
 
+
 oxm_types = [
     oxm_fields.OpenFlowBasic('in_port', 0, type_desc.Int4),
     oxm_fields.OpenFlowBasic('in_phy_port', 1, type_desc.Int4),
diff --git a/ryu/ofproto/ofproto_v1_3.py b/ryu/ofproto/ofproto_v1_3.py
index 9fedae26..d599c1cb 100644
--- a/ryu/ofproto/ofproto_v1_3.py
+++ b/ryu/ofproto/ofproto_v1_3.py
@@ -1180,6 +1180,7 @@ def oxm_tlv_header_extract_length(header):
         length = header & 0xff
     return length
 
+
 oxm_types = [
     oxm_fields.OpenFlowBasic('in_port', 0, type_desc.Int4),
     oxm_fields.OpenFlowBasic('in_phy_port', 1, type_desc.Int4),
diff --git a/ryu/ofproto/ofproto_v1_4.py b/ryu/ofproto/ofproto_v1_4.py
index d1c48225..d332817b 100644
--- a/ryu/ofproto/ofproto_v1_4.py
+++ b/ryu/ofproto/ofproto_v1_4.py
@@ -349,6 +349,7 @@ def oxm_tlv_header_extract_length(header):
         length = header & 0xff
     return length
 
+
 oxm_types = [
     oxm_fields.OpenFlowBasic('in_port', 0, type_desc.Int4),
     oxm_fields.OpenFlowBasic('in_phy_port', 1, type_desc.Int4),
diff --git a/ryu/ofproto/ofproto_v1_5.py b/ryu/ofproto/ofproto_v1_5.py
index 83531845..b1544ac6 100644
--- a/ryu/ofproto/ofproto_v1_5.py
+++ b/ryu/ofproto/ofproto_v1_5.py
@@ -386,6 +386,7 @@ def oxm_tlv_header_extract_length(header):
         length = header & 0xff
     return length
 
+
 oxm_types = [
     oxm_fields.OpenFlowBasic('in_port', 0, type_desc.Int4),
     oxm_fields.OpenFlowBasic('in_phy_port', 1, type_desc.Int4),
@@ -457,6 +458,7 @@ def oxs_tlv_header(field, length):
 def oxs_tlv_header_extract_length(header):
     return header & 0xff
 
+
 oxs_types = [
     oxs_fields.OpenFlowBasic('duration', 0, type_desc.Int4Double),
     oxs_fields.OpenFlowBasic('idle_time', 1, type_desc.Int4Double),
diff --git a/ryu/services/protocols/bgp/core_manager.py b/ryu/services/protocols/bgp/core_manager.py
index fbee25f4..d61824c2 100644
--- a/ryu/services/protocols/bgp/core_manager.py
+++ b/ryu/services/protocols/bgp/core_manager.py
@@ -69,5 +69,6 @@ class _CoreManager(Activity):
         self._check_started()
         return self._vrfs_conf
 
+
 # _CoreManager instance that manages core bgp service and configuration data.
 CORE_MANAGER = _CoreManager()
diff --git a/ryu/services/protocols/bgp/info_base/l2vpnfs.py b/ryu/services/protocols/bgp/info_base/l2vpnfs.py
index d612cc74..64b40fca 100644
--- a/ryu/services/protocols/bgp/info_base/l2vpnfs.py
+++ b/ryu/services/protocols/bgp/info_base/l2vpnfs.py
@@ -58,7 +58,7 @@ class L2VPNFlowSpecPath(VpnPath):
         # Set dummy IP address.
         kwargs['nexthop'] = '0.0.0.0'
         super(L2VPNFlowSpecPath, self).__init__(*args, **kwargs)
-        from ryu.services.protocols.bgp.info_base.vrfl2vpnfs import(
+        from ryu.services.protocols.bgp.info_base.vrfl2vpnfs import (
             L2vpnFlowSpecPath)
         self.VRF_PATH_CLASS = L2vpnFlowSpecPath
         # Because the L2VPN Flow Specification does not require nexthop,
diff --git a/ryu/services/protocols/bgp/info_base/vpnv4fs.py b/ryu/services/protocols/bgp/info_base/vpnv4fs.py
index e87196c2..64511444 100644
--- a/ryu/services/protocols/bgp/info_base/vpnv4fs.py
+++ b/ryu/services/protocols/bgp/info_base/vpnv4fs.py
@@ -58,7 +58,7 @@ class VPNv4FlowSpecPath(VpnPath):
         # Set dummy IP address.
         kwargs['nexthop'] = '0.0.0.0'
         super(VPNv4FlowSpecPath, self).__init__(*args, **kwargs)
-        from ryu.services.protocols.bgp.info_base.vrf4fs import(
+        from ryu.services.protocols.bgp.info_base.vrf4fs import (
             Vrf4FlowSpecPath)
         self.VRF_PATH_CLASS = Vrf4FlowSpecPath
         # Because the IPv4 Flow Specification does not require nexthop,
diff --git a/ryu/services/protocols/bgp/info_base/vpnv6fs.py b/ryu/services/protocols/bgp/info_base/vpnv6fs.py
index 8f2a5dc3..5078442e 100644
--- a/ryu/services/protocols/bgp/info_base/vpnv6fs.py
+++ b/ryu/services/protocols/bgp/info_base/vpnv6fs.py
@@ -58,7 +58,7 @@ class VPNv6FlowSpecPath(VpnPath):
         # Set dummy IP address.
         kwargs['nexthop'] = '::'
         super(VPNv6FlowSpecPath, self).__init__(*args, **kwargs)
-        from ryu.services.protocols.bgp.info_base.vrf6fs import(
+        from ryu.services.protocols.bgp.info_base.vrf6fs import (
             Vrf6FlowSpecPath)
         self.VRF_PATH_CLASS = Vrf6FlowSpecPath
         # Because the IPv6 Flow Specification does not require nexthop,
diff --git a/ryu/services/protocols/bgp/operator/ssh.py b/ryu/services/protocols/bgp/operator/ssh.py
index cb2f63b4..5690f674 100644
--- a/ryu/services/protocols/bgp/operator/ssh.py
+++ b/ryu/services/protocols/bgp/operator/ssh.py
@@ -516,4 +516,5 @@ class Cli(Activity):
         server = hub.StreamServer(listen_info, ssh_server_factory)
         server.serve_forever()
 
+
 SSH_CLI_CONTROLLER = Cli()
diff --git a/ryu/services/protocols/bgp/operator/views/bgp.py b/ryu/services/protocols/bgp/operator/views/bgp.py
index b116ee1d..9309e6c3 100644
--- a/ryu/services/protocols/bgp/operator/views/bgp.py
+++ b/ryu/services/protocols/bgp/operator/views/bgp.py
@@ -278,9 +278,11 @@ class RouteFamilyView(OperatorDetailView):
     afi = fields.DataField('afi')
     safi = fields.DataField('safi')
 
+
 ##################################################################
 # Declarations of list and dict views based on detail views above
 ##################################################################
+
 PeerListView = create_list_view_class(PeerDetailView, 'PeerListView')
 PeerDictView = create_dict_view_class(PeerDetailView, 'PeerDictView')
 
diff --git a/ryu/services/protocols/bgp/processor.py b/ryu/services/protocols/bgp/processor.py
index c65e9b82..789192ea 100644
--- a/ryu/services/protocols/bgp/processor.py
+++ b/ryu/services/protocols/bgp/processor.py
@@ -154,6 +154,7 @@ class BgpProcessor(Activity):
         # Wake-up processing thread if sleeping.
         self.dest_que_evt.set()
 
+
 # =============================================================================
 # Best path computation related utilities.
 # =============================================================================
diff --git a/ryu/services/protocols/bgp/rtconf/neighbors.py b/ryu/services/protocols/bgp/rtconf/neighbors.py
index 8ebd1f50..86e04b39 100644
--- a/ryu/services/protocols/bgp/rtconf/neighbors.py
+++ b/ryu/services/protocols/bgp/rtconf/neighbors.py
@@ -224,6 +224,7 @@ def valid_prefix_filter(filter_):
     le = filter_.get('le', None)
     return PrefixFilter(prefix, policy, ge=ge, le=le)
 
+
 PREFIX_FILTER = 'prefix_filter'
 
 SUPPORTED_FILTER_VALIDATORS = {
diff --git a/ryu/services/protocols/zebra/db/base.py b/ryu/services/protocols/zebra/db/base.py
index 0e20b70d..deda9916 100644
--- a/ryu/services/protocols/zebra/db/base.py
+++ b/ryu/services/protocols/zebra/db/base.py
@@ -35,6 +35,7 @@ def _repr(self):
          for k, v in self.__dict__.items() if not k.startswith('_')])
     return "%s(%s)" % (self.__class__.__name__, m)
 
+
 Base.__repr__ = _repr
 
 
diff --git a/ryu/tests/packet_data_generator3/gen.py b/ryu/tests/packet_data_generator3/gen.py
index cab3e805..aa5c2b7d 100644
--- a/ryu/tests/packet_data_generator3/gen.py
+++ b/ryu/tests/packet_data_generator3/gen.py
@@ -292,6 +292,7 @@ class MyHandler(socketserver.BaseRequestHandler):
 class MyVerboseHandler(MyHandler):
     verbose = True
 
+
 if __name__ == '__main__':
     optlist, args = getopt.getopt(sys.argv[1:], 'dvo:')
     debug = False
diff --git a/ryu/tests/unit/app/test_ofctl_rest.py b/ryu/tests/unit/app/test_ofctl_rest.py
index 5b7a5be7..4d09821e 100644
--- a/ryu/tests/unit/app/test_ofctl_rest.py
+++ b/ryu/tests/unit/app/test_ofctl_rest.py
@@ -131,6 +131,7 @@ def _add_tests():
             )
             test_lib.add_method(Test_ofctl_rest, name, f)
 
+
 _add_tests()
 
 if __name__ == "__main__":
diff --git a/ryu/tests/unit/app/test_ws_topology.py b/ryu/tests/unit/app/test_ws_topology.py
index 6eaaa0e5..6078ff7c 100644
--- a/ryu/tests/unit/app/test_ws_topology.py
+++ b/ryu/tests/unit/app/test_ws_topology.py
@@ -50,5 +50,6 @@ class Test_ws_topology(unittest.TestCase):
         rpc_client_mock1.get_proxy.assert_called_once_with()
         rpc_client_mock2.get_proxy.assert_called_once_with()
 
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/ryu/tests/unit/ofproto/test_parser.py b/ryu/tests/unit/ofproto/test_parser.py
index 081500ad..817ebc3c 100644
--- a/ryu/tests/unit/ofproto/test_parser.py
+++ b/ryu/tests/unit/ofproto/test_parser.py
@@ -307,4 +307,5 @@ def _add_tests():
     assert (cases ==
             set(unittest.defaultTestLoader.getTestCaseNames(Test_Parser)))
 
+
 _add_tests()
diff --git a/ryu/tests/unit/ofproto/test_parser_compat.py b/ryu/tests/unit/ofproto/test_parser_compat.py
index dcca56bd..08be7583 100644
--- a/ryu/tests/unit/ofproto/test_parser_compat.py
+++ b/ryu/tests/unit/ofproto/test_parser_compat.py
@@ -157,4 +157,5 @@ def _add_tests():
                               ofpp=ofpp)
         test_lib.add_method(Test_Parser_Compat, method_name, f)
 
+
 _add_tests()
diff --git a/ryu/tests/unit/ofproto/test_parser_ofpmatch.py b/ryu/tests/unit/ofproto/test_parser_ofpmatch.py
index d4dba9ea..bafcc2a9 100644
--- a/ryu/tests/unit/ofproto/test_parser_ofpmatch.py
+++ b/ryu/tests/unit/ofproto/test_parser_ofpmatch.py
@@ -287,4 +287,5 @@ def _add_tests():
                         test_lib.add_method(Test_Parser_OFPMatch,
                                             method_name, f)
 
+
 _add_tests()
diff --git a/ryu/tests/unit/ofproto/test_parser_ofpstats.py b/ryu/tests/unit/ofproto/test_parser_ofpstats.py
index 0ce428ab..b14bb9de 100644
--- a/ryu/tests/unit/ofproto/test_parser_ofpstats.py
+++ b/ryu/tests/unit/ofproto/test_parser_ofpstats.py
@@ -204,4 +204,5 @@ def _add_tests():
                     test_lib.add_method(Test_Parser_OFPStats,
                                         method_name, f)
 
+
 _add_tests()
diff --git a/ryu/tests/unit/packet/test_ipv6.py b/ryu/tests/unit/packet/test_ipv6.py
index 455dc8c3..e62ba042 100644
--- a/ryu/tests/unit/packet/test_ipv6.py
+++ b/ryu/tests/unit/packet/test_ipv6.py
@@ -795,13 +795,13 @@ class Test_routing(unittest.TestCase):
         not_implemented_buf = struct.pack(
             '!BBBBBB2x', 0, 6, ipv6.routing.ROUTING_TYPE_2, 0, 0, 0)
         instance = ipv6.routing.parser(not_implemented_buf)
-        assert None == instance
+        assert None is instance
 
     def test_invalid_type(self):
         invalid_type = 99
         invalid_buf = struct.pack('!BBBBBB2x', 0, 6, invalid_type, 0, 0, 0)
         instance = ipv6.routing.parser(invalid_buf)
-        assert None == instance
+        assert None is instance
 
 
 class Test_routing_type3(unittest.TestCase):
diff --git a/ryu/tests/unit/packet/test_slow.py b/ryu/tests/unit/packet/test_slow.py
index 9e077fd2..3ce9d450 100644
--- a/ryu/tests/unit/packet/test_slow.py
+++ b/ryu/tests/unit/packet/test_slow.py
@@ -147,16 +147,16 @@ class Test_slow(unittest.TestCase):
         not_implemented_buf = pack(
             slow._PACK_STR, SLOW_SUBTYPE_MARKER) + self.buf[1:]
         (instance, nexttype, last) = slow.parser(not_implemented_buf)
-        assert None == instance
-        assert None == nexttype
-        assert None != last
+        assert instance is None
+        assert nexttype is None
+        assert last is not None
 
     def test_invalid_subtype(self):
         invalid_buf = b'\xff' + self.buf[1:]
         (instance, nexttype, last) = slow.parser(invalid_buf)
-        assert None == instance
-        assert None == nexttype
-        assert None != last
+        assert instance is None
+        assert nexttype is None
+        assert last is not None
 
 
 class Test_lacp(unittest.TestCase):
diff --git a/ryu/tests/unit/test_requirements.py b/ryu/tests/unit/test_requirements.py
index 7bfbd3f4..9f50a518 100644
--- a/ryu/tests/unit/test_requirements.py
+++ b/ryu/tests/unit/test_requirements.py
@@ -57,6 +57,7 @@ def _get_requirements(files):
 
     return requirements
 
+
 OPENSTACK_REQUIREMENTS = _get_requirements(OPENSTACK_REQUIREMENTS_FILES)
 RYU_REQUIREMENTS = _get_requirements(RYU_REQUIREMENTS_FILES)
 
diff --git a/ryu/topology/api.py b/ryu/topology/api.py
index cd72b84b..e4fb2f1c 100644
--- a/ryu/topology/api.py
+++ b/ryu/topology/api.py
@@ -43,4 +43,5 @@ def get_host(app, dpid=None):
 def get_all_host(app):
     return get_host(app)
 
+
 app_manager.require_app('ryu.topology.switches', api_style=True)