diff --git a/deluge/bencode.py b/deluge/bencode.py
index 2cb30f5a1..420ccf646 100644
--- a/deluge/bencode.py
+++ b/deluge/bencode.py
@@ -147,9 +147,9 @@ encode_func[bool] = encode_bool
 encode_func[str] = encode_string
 encode_func[bytes] = encode_bytes
 if PY2:
-    encode_func[long] = encode_int
+    encode_func[long] = encode_int  # noqa: F821
     encode_func[str] = encode_bytes
-    encode_func[unicode] = encode_string
+    encode_func[unicode] = encode_string  # noqa: F821
 
 
 def bencode(x):
diff --git a/deluge/common.py b/deluge/common.py
index e9f33036c..c1c1d641b 100644
--- a/deluge/common.py
+++ b/deluge/common.py
@@ -758,7 +758,7 @@ def get_magnet_info(uri):
     """
 
     tr0_param = 'tr.'
-    tr0_param_regex = re.compile('^tr.(\d+)=(\S+)')
+    tr0_param_regex = re.compile(r'^tr.(\d+)=(\S+)')
     if not uri.startswith(MAGNET_SCHEME):
         return {}
 
diff --git a/deluge/component.py b/deluge/component.py
index 72aa3246a..c7ba83d91 100644
--- a/deluge/component.py
+++ b/deluge/component.py
@@ -13,12 +13,11 @@ import logging
 import traceback
 from collections import defaultdict
 
+from six import string_types
 from twisted.internet import reactor
 from twisted.internet.defer import DeferredList, fail, maybeDeferred, succeed
 from twisted.internet.task import LoopingCall, deferLater
 
-from deluge.common import PY2
-
 log = logging.getLogger(__name__)
 
 
@@ -325,7 +324,7 @@ class ComponentRegistry(object):
         # Start all the components if names is empty
         if not names:
             names = list(self.components)
-        elif isinstance(names, str if not PY2 else basestring):
+        elif isinstance(names, string_types):
             names = [names]
 
         def on_depends_started(result, name):
@@ -359,7 +358,7 @@ class ComponentRegistry(object):
         """
         if not names:
             names = list(self.components)
-        elif isinstance(names, str if not PY2 else basestring):
+        elif isinstance(names, string_types):
             names = [names]
 
         def on_dependents_stopped(result, name):
@@ -399,7 +398,7 @@ class ComponentRegistry(object):
         """
         if not names:
             names = list(self.components)
-        elif isinstance(names, str if not PY2 else basestring):
+        elif isinstance(names, string_types):
             names = [names]
 
         deferreds = []
@@ -425,7 +424,7 @@ class ComponentRegistry(object):
         """
         if not names:
             names = list(self.components)
-        elif isinstance(names, str if not PY2 else basestring):
+        elif isinstance(names, string_types):
             names = [names]
 
         deferreds = []
diff --git a/deluge/core/core.py b/deluge/core/core.py
index 3c3b6b331..47717f5c6 100644
--- a/deluge/core/core.py
+++ b/deluge/core/core.py
@@ -18,6 +18,7 @@ import tempfile
 import threading
 from base64 import b64decode, b64encode
 
+from six import string_types
 from twisted.internet import defer, reactor, task
 from twisted.web.client import Agent, readBody
 
@@ -25,7 +26,6 @@ import deluge.common
 import deluge.component as component
 from deluge import path_chooser_common
 from deluge._libtorrent import LT_VERSION, lt
-from deluge.common import PY2
 from deluge.configmanager import ConfigManager, get_config_dir
 from deluge.core.alertmanager import AlertManager
 from deluge.core.authmanager import (
@@ -666,7 +666,7 @@ class Core(component.Component):
     def pause_torrent(self, torrent_id):
         """Pauses a torrent"""
         log.debug('Pausing: %s', torrent_id)
-        if not isinstance(torrent_id, str if not PY2 else basestring):
+        if not isinstance(torrent_id, string_types):
             self.pause_torrents(torrent_id)
         else:
             self.torrentmanager[torrent_id].pause()
@@ -717,7 +717,7 @@ class Core(component.Component):
     def resume_torrent(self, torrent_id):
         """Resumes a torrent"""
         log.debug('Resuming: %s', torrent_id)
-        if not isinstance(torrent_id, str if not PY2 else basestring):
+        if not isinstance(torrent_id, string_types):
             self.resume_torrents(torrent_id)
         else:
             self.torrentmanager[torrent_id].resume()
@@ -900,7 +900,7 @@ class Core(component.Component):
         if 'owner' in options and not self.authmanager.has_account(options['owner']):
             raise DelugeError('Username "%s" is not known.' % options['owner'])
 
-        if isinstance(torrent_ids, str if not PY2 else basestring):
+        if isinstance(torrent_ids, string_types):
             torrent_ids = [torrent_ids]
 
         for torrent_id in torrent_ids:
diff --git a/deluge/core/filtermanager.py b/deluge/core/filtermanager.py
index 82ded3268..9d8964689 100644
--- a/deluge/core/filtermanager.py
+++ b/deluge/core/filtermanager.py
@@ -11,8 +11,10 @@ from __future__ import unicode_literals
 
 import logging
 
+from six import string_types
+
 import deluge.component as component
-from deluge.common import PY2, TORRENT_STATE
+from deluge.common import TORRENT_STATE
 
 log = logging.getLogger(__name__)
 
@@ -136,7 +138,7 @@ class FilterManager(component.Component):
 
         # Sanitize input: filter-value must be a list of strings
         for key, value in filter_dict.items():
-            if isinstance(value, str if not PY2 else basestring):
+            if isinstance(value, string_types):
                 filter_dict[key] = [value]
 
         # Optimized filter for id
diff --git a/deluge/tests/__init__.py b/deluge/tests/__init__.py
index 5a1ef6ea2..cc18352b9 100644
--- a/deluge/tests/__init__.py
+++ b/deluge/tests/__init__.py
@@ -10,5 +10,5 @@ else:
     try:
         resource.setrlimit(resource.RLIMIT_NOFILE, (65536, 65536))
     except (ValueError, resource.error) as ex:
-        # print('Failed to raise file descriptor limit:', ex)
-        pass
+        error = 'Failed to raise file descriptor limit: %s' % ex
+        # print(error)
diff --git a/deluge/tests/test_core.py b/deluge/tests/test_core.py
index 1bf5af265..4a990285d 100644
--- a/deluge/tests/test_core.py
+++ b/deluge/tests/test_core.py
@@ -11,6 +11,7 @@ from base64 import b64encode
 from hashlib import sha1 as sha
 
 import pytest
+from six import integer_types
 from twisted.internet import defer, reactor, task
 from twisted.internet.error import CannotListenError
 from twisted.python.failure import Failure
@@ -22,7 +23,6 @@ from twisted.web.static import File
 import deluge.common
 import deluge.component as component
 import deluge.core.torrent
-from deluge.common import PY2
 from deluge.core.core import Core
 from deluge.core.rpcserver import RPCServer
 from deluge.error import AddTorrentError, InvalidTorrentError
@@ -429,7 +429,7 @@ class CoreTestCase(BaseTestCase):
     def test_get_free_space(self):
         space = self.core.get_free_space('.')
         # get_free_space returns long on Python 2 (32-bit).
-        self.assertTrue(isinstance(space, int if not PY2 else (int, long)))
+        self.assertTrue(isinstance(space, integer_types))
         self.assertTrue(space >= 0)
         self.assertEqual(self.core.get_free_space('/someinvalidpath'), -1)
 
diff --git a/deluge/tests/test_files_tab.py b/deluge/tests/test_files_tab.py
index 109f67a02..8e522aa1d 100644
--- a/deluge/tests/test_files_tab.py
+++ b/deluge/tests/test_files_tab.py
@@ -24,7 +24,7 @@ try:
     from deluge.ui.gtkui.files_tab import FilesTab
     from deluge.ui.gtkui.gtkui import DEFAULT_PREFS
     from deluge.ui.gtkui.mainwindow import MainWindow
-except ImportError as err:
+except ImportError:
     libs_available = False
 
 setup_translations()
@@ -101,7 +101,7 @@ class FilesTabTestCase(BaseTestCase):
 
     def test_files_tab2(self):
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\ != / for path names')
         self.filestab.files_list[self.t_id] = (
             {'index': 0, 'path': '1/1/test_10.txt', 'offset': 0, 'size': 13},
             {'index': 1, 'path': 'test_100.txt', 'offset': 13, 'size': 14},
@@ -121,7 +121,7 @@ class FilesTabTestCase(BaseTestCase):
 
     def test_files_tab3(self):
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\ != / for path names')
         self.filestab.files_list[self.t_id] = (
             {'index': 0, 'path': '1/test_10.txt', 'offset': 0, 'size': 13},
             {'index': 1, 'path': 'test_100.txt', 'offset': 13, 'size': 14},
@@ -158,7 +158,7 @@ class FilesTabTestCase(BaseTestCase):
 
     def test_files_tab5(self):
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\ != / for path names')
         self.filestab.files_list[self.t_id] = (
             {'index': 0, 'path': '1/test_10.txt', 'offset': 0, 'size': 13},
             {'index': 1, 'path': '2/test_100.txt', 'offset': 13, 'size': 14},
diff --git a/deluge/tests/test_httpdownloader.py b/deluge/tests/test_httpdownloader.py
index e3746a1ad..e20c541f5 100644
--- a/deluge/tests/test_httpdownloader.py
+++ b/deluge/tests/test_httpdownloader.py
@@ -178,7 +178,7 @@ class DownloadFileTestCase(unittest.TestCase):
     def test_download_with_rename(self):
 
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\  != / for path names')
 
         url = self.get_url('rename?filename=renamed')
         d = download_file(url, fname('original'))
@@ -189,7 +189,7 @@ class DownloadFileTestCase(unittest.TestCase):
     def test_download_with_rename_exists(self):
 
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\  != / for path names')
 
         open(fname('renamed'), 'w').close()
         url = self.get_url('rename?filename=renamed')
@@ -201,7 +201,7 @@ class DownloadFileTestCase(unittest.TestCase):
     def test_download_with_rename_sanitised(self):
 
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\  != / for path names')
 
         url = self.get_url('rename?filename=/etc/passwd')
         d = download_file(url, fname('original'))
diff --git a/deluge/tests/test_metafile.py b/deluge/tests/test_metafile.py
index 20b6b1056..fc6507cb8 100644
--- a/deluge/tests/test_metafile.py
+++ b/deluge/tests/test_metafile.py
@@ -53,7 +53,7 @@ class MetafileTestCase(unittest.TestCase):
 
     def test_save_singlefile(self):
         if windows_check():
-            raise unittest.SkipTest('on windows \ != / for path names')
+            raise unittest.SkipTest('on windows \\ != / for path names')
         tmp_path = tempfile.mkstemp('testdata')[1]
         with open(tmp_path, 'wb') as tmp_file:
             tmp_file.write(b'a' * (2314 * 1024))
diff --git a/deluge/tests/test_torrentview.py b/deluge/tests/test_torrentview.py
index 01a6bd67b..6ff95c8f6 100644
--- a/deluge/tests/test_torrentview.py
+++ b/deluge/tests/test_torrentview.py
@@ -23,7 +23,7 @@ from .basetest import BaseTestCase
 # Allow running other tests without GTKUI dependencies available
 try:
     from gobject import TYPE_UINT64
-except ImportError as err:
+except ImportError:
     libs_available = False
     TYPE_UINT64 = 'Whatever'
 else:
diff --git a/deluge/ui/console/cmdline/commands/config.py b/deluge/ui/console/cmdline/commands/config.py
index 1cbccba88..bd0a1e15f 100644
--- a/deluge/ui/console/cmdline/commands/config.py
+++ b/deluge/ui/console/cmdline/commands/config.py
@@ -57,7 +57,7 @@ def atom(src, token):
         return token[-1].decode('string-escape')
     elif token[1].isalpha():
         # Parse Windows paths e.g. 'C:\\xyz' or 'C:/xyz'.
-        if next()[1] == ':' and next()[1] in '\/':
+        if next()[1] == ':' and next()[1] in '\\/':
             return token[-1].decode('string-escape')
 
     raise SyntaxError('malformed expression (%s)' % token[1])
diff --git a/deluge/ui/console/modes/add_util.py b/deluge/ui/console/modes/add_util.py
index 6ebfd9957..88a24d0d9 100644
--- a/deluge/ui/console/modes/add_util.py
+++ b/deluge/ui/console/modes/add_util.py
@@ -16,6 +16,8 @@ import logging
 import os
 from base64 import b64encode
 
+from six import unichr as chr
+
 import deluge.common
 from deluge.ui.client import client
 from deluge.ui.common import TorrentInfo
@@ -27,16 +29,16 @@ def _bracket_fixup(path):
     if path.find('[') == -1 and path.find(']') == -1:
         return path
     sentinal = 256
-    while path.find(unichr(sentinal)) != -1:
+    while path.find(chr(sentinal)) != -1:
         sentinal += 1
         if sentinal > 65535:
             log.error(
                 'Cannot fix brackets in path, path contains all possible sentinal characters'
             )
             return path
-    newpath = path.replace(']', unichr(sentinal))
+    newpath = path.replace(']', chr(sentinal))
     newpath = newpath.replace('[', '[[]')
-    newpath = newpath.replace(unichr(sentinal), '[]]')
+    newpath = newpath.replace(chr(sentinal), '[]]')
     return newpath
 
 
diff --git a/deluge/ui/console/modes/basemode.py b/deluge/ui/console/modes/basemode.py
index bdaa5dfd5..6d9d847d4 100644
--- a/deluge/ui/console/modes/basemode.py
+++ b/deluge/ui/console/modes/basemode.py
@@ -300,7 +300,7 @@ def add_string(
 
         try:
             screen.addstr(row, col, string.encode(encoding), color)
-        except curses.error as ex:
+        except curses.error:
             # Ignore exception for writing offscreen.
             pass
 
diff --git a/deluge/ui/gtkui/gtkui.py b/deluge/ui/gtkui/gtkui.py
index 16bde8454..d3bafe4d9 100644
--- a/deluge/ui/gtkui/gtkui.py
+++ b/deluge/ui/gtkui/gtkui.py
@@ -31,7 +31,7 @@ from twisted.internet.task import LoopingCall
 try:
     # Install twisted reactor, before any other modules import reactor.
     reactor = gtk2reactor.install()
-except ReactorAlreadyInstalledError as ex:
+except ReactorAlreadyInstalledError:
     # Running unit tests so trial already installed a rector
     from twisted.internet import reactor
 
diff --git a/deluge/ui/ui_entry.py b/deluge/ui/ui_entry.py
index b20be980b..cefce0db5 100644
--- a/deluge/ui/ui_entry.py
+++ b/deluge/ui/ui_entry.py
@@ -117,7 +117,7 @@ def start_ui():
         ui = ui_entrypoints[selected_ui](
             prog='%s %s' % (os.path.basename(sys.argv[0]), selected_ui), ui_args=ui_args
         )
-    except KeyError as ex:
+    except KeyError:
         log.error(
             'Unable to find chosen UI: "%s". Please choose a different UI '
             'or use "--set-default-ui" to change default UI.',