diff --git a/searx/engines/acgsou.py b/searx/engines/acgsou.py
index 553b49b69..a436df283 100644
--- a/searx/engines/acgsou.py
+++ b/searx/engines/acgsou.py
@@ -41,7 +41,6 @@ def response(resp):
         # defaults
         filesize = 0
         magnet_link = "magnet:?xt=urn:btih:{}&tr=http://tracker.acgsou.com:2710/announce"
-        torrent_link = ""
 
         try:
             category = extract_text(result.xpath(xpath_category)[0])
diff --git a/searx/engines/arxiv.py b/searx/engines/arxiv.py
index e54de4a58..6e231c382 100644
--- a/searx/engines/arxiv.py
+++ b/searx/engines/arxiv.py
@@ -61,7 +61,7 @@ def response(resp):
             content = content_string.format(doi_content="", abstract_content=abstract)
 
         if len(content) > 300:
-                    content = content[0:300] + "..."
+            content = content[0:300] + "..."
         # TODO: center snippet on query term
 
         publishedDate = datetime.strptime(entry.xpath('.//published')[0].text, '%Y-%m-%dT%H:%M:%SZ')
diff --git a/searx/engines/base.py b/searx/engines/base.py
index 0114f9798..3648d7ed0 100755
--- a/searx/engines/base.py
+++ b/searx/engines/base.py
@@ -80,10 +80,7 @@ def response(resp):
 
         date = datetime.now()  # needed in case no dcdate is available for an item
         for item in entry:
-            if item.attrib["name"] == "dchdate":
-                harvestDate = item.text
-
-            elif item.attrib["name"] == "dcdate":
+            if item.attrib["name"] == "dcdate":
                 date = item.text
 
             elif item.attrib["name"] == "dctitle":
diff --git a/searx/engines/bing_images.py b/searx/engines/bing_images.py
index 3085e1deb..2bcf82b84 100644
--- a/searx/engines/bing_images.py
+++ b/searx/engines/bing_images.py
@@ -18,7 +18,7 @@ from json import loads
 from searx.utils import match_language
 
 from searx.engines.bing import language_aliases
-from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 
 # engine dependent config
 categories = ['images']
diff --git a/searx/engines/bing_news.py b/searx/engines/bing_news.py
index aeef7d19a..5489c7549 100644
--- a/searx/engines/bing_news.py
+++ b/searx/engines/bing_news.py
@@ -17,7 +17,7 @@ from urllib.parse import urlencode, urlparse, parse_qsl
 from lxml import etree
 from searx.utils import list_get, match_language
 from searx.engines.bing import language_aliases
-from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 
 # engine dependent config
 categories = ['news']
diff --git a/searx/engines/bing_videos.py b/searx/engines/bing_videos.py
index 4393ea590..143c71a3e 100644
--- a/searx/engines/bing_videos.py
+++ b/searx/engines/bing_videos.py
@@ -16,7 +16,7 @@ from urllib.parse import urlencode
 from searx.utils import match_language
 
 from searx.engines.bing import language_aliases
-from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.bing import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 
 categories = ['videos']
 paging = True
diff --git a/searx/engines/currency_convert.py b/searx/engines/currency_convert.py
index 0e91d31e9..f41c135b9 100644
--- a/searx/engines/currency_convert.py
+++ b/searx/engines/currency_convert.py
@@ -41,8 +41,6 @@ def request(query, params):
     from_currency = name_to_iso4217(from_currency.strip())
     to_currency = name_to_iso4217(to_currency.strip())
 
-    q = (from_currency + to_currency).upper()
-
     params['url'] = url.format(from_currency, to_currency)
     params['amount'] = amount
     params['from'] = from_currency
diff --git a/searx/engines/duckduckgo.py b/searx/engines/duckduckgo.py
index 21cd926aa..c1c984623 100644
--- a/searx/engines/duckduckgo.py
+++ b/searx/engines/duckduckgo.py
@@ -49,11 +49,11 @@ correction_xpath = '//div[@id="did_you_mean"]//a'
 
 
 # match query's language to a region code that duckduckgo will accept
-def get_region_code(lang, lang_list=[]):
+def get_region_code(lang, lang_list=None):
     if lang == 'all':
         return None
 
-    lang_code = match_language(lang, lang_list, language_aliases, 'wt-WT')
+    lang_code = match_language(lang, lang_list or [], language_aliases, 'wt-WT')
     lang_parts = lang_code.split('-')
 
     # country code goes first
diff --git a/searx/engines/duckduckgo_definitions.py b/searx/engines/duckduckgo_definitions.py
index 5758022d2..5a7649173 100644
--- a/searx/engines/duckduckgo_definitions.py
+++ b/searx/engines/duckduckgo_definitions.py
@@ -16,7 +16,7 @@ from lxml import html
 from searx import logger
 from searx.data import WIKIDATA_UNITS
 from searx.engines.duckduckgo import language_aliases
-from searx.engines.duckduckgo import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.duckduckgo import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 from searx.utils import extract_text, html_to_text, match_language, get_string_replaces_function
 from searx.external_urls import get_external_url, get_earth_coordinates_url, area_to_osm_zoom
 
diff --git a/searx/engines/duckduckgo_images.py b/searx/engines/duckduckgo_images.py
index 943b74880..438a8d54c 100644
--- a/searx/engines/duckduckgo_images.py
+++ b/searx/engines/duckduckgo_images.py
@@ -16,7 +16,7 @@
 from json import loads
 from urllib.parse import urlencode
 from searx.engines.duckduckgo import get_region_code
-from searx.engines.duckduckgo import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.duckduckgo import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 from searx.poolrequests import get
 
 # engine dependent config
diff --git a/searx/engines/filecrop.py b/searx/engines/filecrop.py
index eef5be6e8..0331e7b19 100644
--- a/searx/engines/filecrop.py
+++ b/searx/engines/filecrop.py
@@ -8,7 +8,7 @@ search_url = url + '/search.php?{query}&size_i=0&size_f=100000000&engine_r=1&eng
 paging = True
 
 
-class FilecropResultParser(HTMLParser):
+class FilecropResultParser(HTMLParser):  # pylint: disable=W0223  # (see https://bugs.python.org/issue31844)
 
     def __init__(self):
         HTMLParser.__init__(self)
diff --git a/searx/engines/google_images.py b/searx/engines/google_images.py
index 9669d81c3..a3daf6070 100644
--- a/searx/engines/google_images.py
+++ b/searx/engines/google_images.py
@@ -29,10 +29,7 @@ from lxml import html
 from flask_babel import gettext
 from searx import logger
 from searx.utils import extract_text, eval_xpath
-from searx.engines.google import _fetch_supported_languages, supported_languages_url  # NOQA
-
-# pylint: disable=unused-import
-# pylint: enable=unused-import
+from searx.engines.google import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 
 from searx.engines.google import (
     get_lang_country,
diff --git a/searx/engines/google_news.py b/searx/engines/google_news.py
index 6cfc0c8e7..f1b7cfa79 100644
--- a/searx/engines/google_news.py
+++ b/searx/engines/google_news.py
@@ -13,7 +13,7 @@
 from urllib.parse import urlencode
 from lxml import html
 from searx.utils import match_language
-from searx.engines.google import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.google import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 
 # search-url
 categories = ['news']
diff --git a/searx/engines/peertube.py b/searx/engines/peertube.py
index 58ff38c02..e43b2a6b7 100644
--- a/searx/engines/peertube.py
+++ b/searx/engines/peertube.py
@@ -90,6 +90,5 @@ def response(resp):
 
 
 def _fetch_supported_languages(resp):
-    ret_val = {}
     peertube_languages = list(loads(resp.text).keys())
     return peertube_languages
diff --git a/searx/engines/pubmed.py b/searx/engines/pubmed.py
index 7eb2e92f9..07c45709e 100644
--- a/searx/engines/pubmed.py
+++ b/searx/engines/pubmed.py
@@ -81,7 +81,7 @@ def response(resp):
             pass
 
         if len(content) > 300:
-                    content = content[0:300] + "..."
+            content = content[0:300] + "..."
         # TODO: center snippet on query term
 
         res_dict = {'url': url,
diff --git a/searx/engines/yahoo_news.py b/searx/engines/yahoo_news.py
index 11941cfe1..793d1104a 100644
--- a/searx/engines/yahoo_news.py
+++ b/searx/engines/yahoo_news.py
@@ -14,7 +14,7 @@ from datetime import datetime, timedelta
 from urllib.parse import urlencode
 from lxml import html
 from searx.engines.yahoo import parse_url, language_aliases
-from searx.engines.yahoo import _fetch_supported_languages, supported_languages_url  # NOQA
+from searx.engines.yahoo import _fetch_supported_languages, supported_languages_url  # NOQA # pylint: disable=unused-import
 from dateutil import parser
 from searx.utils import extract_text, extract_url, match_language
 
diff --git a/searx/plugins/__init__.py b/searx/plugins/__init__.py
index fe7ae0578..661b4f6aa 100644
--- a/searx/plugins/__init__.py
+++ b/searx/plugins/__init__.py
@@ -158,8 +158,8 @@ def prepare_package_resources(pkg, name):
 
 def sha_sum(filename):
     with open(filename, "rb") as f:
-        bytes = f.read()
-        return sha256(bytes).hexdigest()
+        file_content_bytes = f.read()
+        return sha256(file_content_bytes).hexdigest()
 
 
 plugins = PluginStore()
diff --git a/searx/query.py b/searx/query.py
index 7effda15a..422cd57b5 100644
--- a/searx/query.py
+++ b/searx/query.py
@@ -92,15 +92,15 @@ class RawTextQuery:
                         or lang == english_name
                         or lang.replace('-', ' ') == country)\
                        and lang not in self.languages:
-                            searx_query_part = True
-                            lang_parts = lang_id.split('-')
-                            if len(lang_parts) == 2:
-                                self.languages.append(lang_parts[0] + '-' + lang_parts[1].upper())
-                            else:
-                                self.languages.append(lang_id)
-                            # to ensure best match (first match is not necessarily the best one)
-                            if lang == lang_id:
-                                break
+                        searx_query_part = True
+                        lang_parts = lang_id.split('-')
+                        if len(lang_parts) == 2:
+                            self.languages.append(lang_parts[0] + '-' + lang_parts[1].upper())
+                        else:
+                            self.languages.append(lang_id)
+                        # to ensure best match (first match is not necessarily the best one)
+                        if lang == lang_id:
+                            break
 
                 # user may set a valid, yet not selectable language
                 if VALID_LANGUAGE_CODE.match(lang):
diff --git a/searx/results.py b/searx/results.py
index e0bbe3358..46f44e1ad 100644
--- a/searx/results.py
+++ b/searx/results.py
@@ -298,7 +298,7 @@ class ResultContainer:
         gresults = []
         categoryPositions = {}
 
-        for i, res in enumerate(results):
+        for res in results:
             # FIXME : handle more than one category per engine
             res['category'] = engines[res['engine']].categories[0]
 
diff --git a/searx/search.py b/searx/search.py
index b8ada3901..a3b80249e 100644
--- a/searx/search.py
+++ b/searx/search.py
@@ -43,9 +43,8 @@ else:
         logger.info('max_request_timeout={0} second(s)'.format(max_request_timeout))
     else:
         logger.critical('outgoing.max_request_timeout if defined has to be float')
-        from sys import exit
-
-        exit(1)
+        import sys
+        sys.exit(1)
 
 
 class EngineRef:
diff --git a/searx/utils.py b/searx/utils.py
index 4eed87f21..738f2c4d5 100644
--- a/searx/utils.py
+++ b/searx/utils.py
@@ -52,7 +52,7 @@ class HTMLTextExtractorException(Exception):
     pass
 
 
-class HTMLTextExtractor(HTMLParser):
+class HTMLTextExtractor(HTMLParser):  # pylint: disable=W0223  # (see https://bugs.python.org/issue31844)
 
     def __init__(self):
         HTMLParser.__init__(self)
@@ -74,18 +74,18 @@ class HTMLTextExtractor(HTMLParser):
     def is_valid_tag(self):
         return not self.tags or self.tags[-1] not in blocked_tags
 
-    def handle_data(self, d):
+    def handle_data(self, data):
         if not self.is_valid_tag():
             return
-        self.result.append(d)
+        self.result.append(data)
 
-    def handle_charref(self, number):
+    def handle_charref(self, name):
         if not self.is_valid_tag():
             return
-        if number[0] in ('x', 'X'):
-            codepoint = int(number[1:], 16)
+        if name[0] in ('x', 'X'):
+            codepoint = int(name[1:], 16)
         else:
-            codepoint = int(number)
+            codepoint = int(name)
         self.result.append(chr(codepoint))
 
     def handle_entityref(self, name):
@@ -380,7 +380,7 @@ def _get_lang_to_lc_dict(lang_list):
     return value
 
 
-def _match_language(lang_code, lang_list=[], custom_aliases={}):
+def _match_language(lang_code, lang_list=[], custom_aliases={}):  # pylint: disable=W0102
     """auxiliary function to match lang_code in lang_list"""
     # replace language code with a custom alias if necessary
     if lang_code in custom_aliases:
@@ -403,7 +403,7 @@ def _match_language(lang_code, lang_list=[], custom_aliases={}):
     return _get_lang_to_lc_dict(lang_list).get(lang_code, None)
 
 
-def match_language(locale_code, lang_list=[], custom_aliases={}, fallback='en-US'):
+def match_language(locale_code, lang_list=[], custom_aliases={}, fallback='en-US'):  # pylint: disable=W0102
     """get the language code from lang_list that best matches locale_code"""
     # try to get language from given locale_code
     language = _match_language(locale_code, lang_list, custom_aliases)
diff --git a/searx/webapp.py b/searx/webapp.py
index 6186fe6ce..e73322a77 100755
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -466,7 +466,7 @@ def pre_request():
     else:
         try:
             preferences.parse_dict(request.form)
-        except Exception as e:
+        except Exception:
             logger.exception('invalid settings')
             request.errors.append(gettext('Invalid settings'))
 
@@ -819,7 +819,6 @@ def preferences():
 
     # render preferences
     image_proxy = request.preferences.get_value('image_proxy')
-    lang = request.preferences.get_value('language')
     disabled_engines = request.preferences.engines.get_disabled()
     allowed_plugins = request.preferences.plugins.get_enabled()
 
diff --git a/tests/unit/test_plugins.py b/tests/unit/test_plugins.py
index 969630c40..9ef4cd692 100644
--- a/tests/unit/test_plugins.py
+++ b/tests/unit/test_plugins.py
@@ -31,10 +31,10 @@ class PluginStoreTest(SearxTestCase):
         request = Mock()
         store.call([], 'asdf', request, Mock())
 
-        self.assertFalse(testplugin.asdf.called)
+        self.assertFalse(testplugin.asdf.called)  # pylint: disable=E1101
 
         store.call([testplugin], 'asdf', request, Mock())
-        self.assertTrue(testplugin.asdf.called)
+        self.assertTrue(testplugin.asdf.called)  # pylint: disable=E1101
 
 
 class SelfIPTest(SearxTestCase):
diff --git a/tests/unit/test_preferences.py b/tests/unit/test_preferences.py
index bee436027..510d4985a 100644
--- a/tests/unit/test_preferences.py
+++ b/tests/unit/test_preferences.py
@@ -5,8 +5,8 @@ from searx.testing import SearxTestCase
 
 class PluginStub:
 
-    def __init__(self, id, default_on):
-        self.id = id
+    def __init__(self, plugin_id, default_on):
+        self.id = plugin_id
         self.default_on = default_on
 
 
@@ -15,11 +15,11 @@ class TestSettings(SearxTestCase):
 
     def test_map_setting_invalid_initialization(self):
         with self.assertRaises(MissingArgumentException):
-            setting = MapSetting(3, wrong_argument={'0': 0})
+            MapSetting(3, wrong_argument={'0': 0})
 
     def test_map_setting_invalid_default_value(self):
         with self.assertRaises(ValidationException):
-            setting = MapSetting(3, map={'dog': 1, 'bat': 2})
+            MapSetting(3, map={'dog': 1, 'bat': 2})
 
     def test_map_setting_invalid_choice(self):
         setting = MapSetting(2, map={'dog': 1, 'bat': 2})
@@ -36,18 +36,14 @@ class TestSettings(SearxTestCase):
         setting.parse('bat')
         self.assertEqual(setting.get_value(), 2)
 
-    def test_enum_setting_invalid_initialization(self):
-        with self.assertRaises(MissingArgumentException):
-            setting = EnumStringSetting('cat', wrong_argument=[0, 1, 2])
-
     # enum settings
     def test_enum_setting_invalid_initialization(self):
         with self.assertRaises(MissingArgumentException):
-            setting = EnumStringSetting('cat', wrong_argument=[0, 1, 2])
+            EnumStringSetting('cat', wrong_argument=[0, 1, 2])
 
     def test_enum_setting_invalid_default_value(self):
         with self.assertRaises(ValidationException):
-            setting = EnumStringSetting(3, choices=[0, 1, 2])
+            EnumStringSetting(3, choices=[0, 1, 2])
 
     def test_enum_setting_invalid_choice(self):
         setting = EnumStringSetting(0, choices=[0, 1, 2])
@@ -67,11 +63,11 @@ class TestSettings(SearxTestCase):
     # multiple choice settings
     def test_multiple_setting_invalid_initialization(self):
         with self.assertRaises(MissingArgumentException):
-            setting = MultipleChoiceSetting(['2'], wrong_argument=['0', '1', '2'])
+            MultipleChoiceSetting(['2'], wrong_argument=['0', '1', '2'])
 
     def test_multiple_setting_invalid_default_value(self):
         with self.assertRaises(ValidationException):
-            setting = MultipleChoiceSetting(['3', '4'], choices=['0', '1', '2'])
+            MultipleChoiceSetting(['3', '4'], choices=['0', '1', '2'])
 
     def test_multiple_setting_invalid_choice(self):
         setting = MultipleChoiceSetting(['1', '2'], choices=['0', '1', '2'])