diff --git a/.sonar/analyse.py b/.sonar/analyse.py
index 34253533fd0..9a25120723b 100644
--- a/.sonar/analyse.py
+++ b/.sonar/analyse.py
@@ -13,7 +13,7 @@
 # These env varialble should be set by Jenkins.
 SERVER_URL = os.environ.get('SONAR_SERVER_URL', "https://sonarcloud.io")
 PROJECT_KEY = os.environ.get('PROJECT_KEY', "org.sonarqube:tribler")
-PR_COMMIT = os.environ.get('ghprbActualCommit', u'')
+PR_COMMIT = os.environ.get('ghprbActualCommit', '')
 TASK_PATH = os.path.join(os.environ.get('WORKSPACE', os.getcwd()), '.scannerwork', 'report-task.txt')
 
 task_status_url = None
@@ -56,12 +56,12 @@
     json_response = requests.get(pr_analysis_url)
     data = json.loads(json_response.text)
 
-    for pull_request in data[u'pullRequests']:
-        print("Matching analysis:", pull_request[u'key'], PR_COMMIT, pull_request[u'key'] == PR_COMMIT)
+    for pull_request in data['pullRequests']:
+        print("Matching analysis:", pull_request['key'], PR_COMMIT, pull_request['key'] == PR_COMMIT)
         # If there is analysis result for the PR commit with status OK, then exit with success status (0)
-        if pull_request[u'key'] == PR_COMMIT:
-            print("Quality Gate:", pull_request[u'status'])
-            if pull_request[u'status'][u'qualityGateStatus'] == u'OK':
+        if pull_request['key'] == PR_COMMIT:
+            print("Quality Gate:", pull_request['status'])
+            if pull_request['status']['qualityGateStatus'] == 'OK':
                 print("Status: OK")
                 break
             else:
diff --git a/doc/conf.py b/doc/conf.py
index 46f37a5aefc..ec18fa0b5ea 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -26,6 +26,14 @@
 
 # root_dir = Path(__file__).parent.parent
 
+def _add_root_endpoint(add_endpoint):
+    def _add_endpoint(self, path, ep):
+        if path in ['/ipv8', '/market', '/wallets']:
+            return None
+        return add_endpoint(self, path, ep)
+    
+    return _add_endpoint
+
 root_dir = os.path.abspath(os.path.join(os.path.dirname(__name__), '..'))
 tribler_source_dirs = [
     os.path.join(root_dir, "src"),
@@ -49,8 +57,7 @@
     from tribler.core.components.restapi.rest.root_endpoint import RootEndpoint
 
     add_endpoint = RootEndpoint.add_endpoint
-    RootEndpoint.add_endpoint = lambda self, path, ep: add_endpoint(self, path, ep) \
-        if path not in ['/ipv8', '/market', '/wallets'] else None
+    RootEndpoint.add_endpoint = _add_root_endpoint(add_endpoint=add_endpoint)
 
     # Extract Swagger docs
     from extract_swagger import extract_swagger
@@ -93,18 +100,18 @@
 master_doc = 'index'
 
 # General information about the project.
-project = u'Tribler'
-copyright = u'2020, Tribler devs'
-author = u'Tribler devs'
+project = 'Tribler'
+copyright = '2020, Tribler devs'
+author = 'Tribler devs'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = u'7.5'
+version = '7.5'
 # The full version, including alpha/beta/rc tags.
-release = u'7.5.0'
+release = '7.5.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -177,7 +184,7 @@
 # The name for this set of Sphinx documents.
 # "<project> v<release> documentation" by default.
 #
-# html_title = u'Tribler v6.6'
+# html_title = 'Tribler v6.6'
 
 # A shorter title for the navigation bar.  Default is the same as html_title.
 #
@@ -303,8 +310,8 @@
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
-    (master_doc, 'Tribler.tex', u'Tribler Documentation',
-     u'Tribler devs', 'manual'),
+    (master_doc, 'Tribler.tex', 'Tribler Documentation',
+     'Tribler devs', 'manual'),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
@@ -339,7 +346,7 @@
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
-    (master_doc, 'tribler', u'Tribler Documentation',
+    (master_doc, 'tribler', 'Tribler Documentation',
      [author], 1)
 ]
 
@@ -354,7 +361,7 @@
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
-    (master_doc, 'Tribler', u'Tribler Documentation',
+    (master_doc, 'Tribler', 'Tribler Documentation',
      author, 'Tribler', 'One line description of project.',
      'Miscellaneous'),
 ]
diff --git a/requirements-build.txt b/requirements-build.txt
index 1774335a82a..f69876dd512 100644
--- a/requirements-build.txt
+++ b/requirements-build.txt
@@ -8,4 +8,4 @@ text-unidecode==1.3; sys_platform == 'darwin'
 defusedxml==0.7.1; sys_platform == 'linux2' or sys_platform == 'linux'
 markupsafe==2.0.1; sys_platform == 'linux2' or sys_platform == 'linux'
 
-requests==2.25.1
\ No newline at end of file
+requests==2.31.0
\ No newline at end of file
diff --git a/src/tribler/core/components/gigachannel/community/gigachannel_community.py b/src/tribler/core/components/gigachannel/community/gigachannel_community.py
index 06bd7f74899..936570e0654 100644
--- a/src/tribler/core/components/gigachannel/community/gigachannel_community.py
+++ b/src/tribler/core/components/gigachannel/community/gigachannel_community.py
@@ -1,3 +1,4 @@
+import operator
 import uuid
 from binascii import unhexlify
 from collections import defaultdict
@@ -47,7 +48,7 @@ def add(self, peer: Peer, channel_pk: bytes, channel_id: int):
         self._peers_channels[peer].add(id_tuple)
 
         if len(channel_peers) > self.max_peers_per_channel:
-            removed_peer = min(channel_peers, key=lambda x: x.last_response)
+            removed_peer = min(channel_peers, key=operator.attrgetter("last_response"))
             channel_peers.remove(removed_peer)
             # Maintain the reverse mapping
             self._peers_channels[removed_peer].remove(id_tuple)
@@ -64,7 +65,10 @@ def remove_peer(self, peer):
     def get_last_seen_peers_for_channel(self, channel_pk: bytes, channel_id: int, limit=None):
         id_tuple = (channel_pk, channel_id)
         channel_peers = self._channels_dict.get(id_tuple, [])
-        return sorted(channel_peers, key=lambda x: x.last_response, reverse=True)[0:limit]
+        last_seen_peers = (
+            sorted(channel_peers, key=operator.attrgetter("last_response"), reverse=True)
+        )
+        return last_seen_peers[0:limit]
 
 
 class GigaChannelCommunity(RemoteQueryCommunity):
diff --git a/src/tribler/core/components/libtorrent/download_manager/download_manager.py b/src/tribler/core/components/libtorrent/download_manager/download_manager.py
index d150bc092e5..857723629fb 100644
--- a/src/tribler/core/components/libtorrent/download_manager/download_manager.py
+++ b/src/tribler/core/components/libtorrent/download_manager/download_manager.py
@@ -248,11 +248,11 @@ def create_session(self, hops=0, store_listen_port=True):
         self._logger.info(f'Dummy mode: {self.dummy_mode}. Hops: {hops}.')
 
         # Elric: Strip out the -rcX, -beta, -whatever tail on the version string.
-        fingerprint = ['TL'] + [int(x) for x in version_id.split('-')[0].split('.')] + [0]
+        fingerprint = ['TL', *map(int, version_id.split('-')[0].split('.')), 0]
         if self.dummy_mode:
             from unittest.mock import Mock
             ltsession = Mock()
-            ltsession.pop_alerts = lambda: {}
+            ltsession.pop_alerts = dict
             ltsession.listen_port = lambda: 123
             ltsession.get_settings = lambda: {"peer_fingerprint": "000"}
         else:
@@ -268,10 +268,10 @@ def create_session(self, hops=0, store_listen_port=True):
             settings['enable_incoming_utp'] = enable_utp
 
             settings['prefer_rc4'] = True
-            settings["listen_interfaces"] = "0.0.0.0:%d" % libtorrent_port
+            settings["listen_interfaces"] = f"0.0.0.0:{libtorrent_port}"
 
             settings['peer_fingerprint'] = self.peer_mid
-            settings['handshake_client_version'] = 'Tribler/' + version_id + '/' + hexlify(self.peer_mid)
+            settings['handshake_client_version'] = f"Tribler/{version_id}/{hexlify(self.peer_mid)}"
         else:
             settings['enable_outgoing_utp'] = True
             settings['enable_incoming_utp'] = True
@@ -281,7 +281,7 @@ def create_session(self, hops=0, store_listen_port=True):
             settings['force_proxy'] = True
 
             # Anon listen port is never used anywhere, so we let Libtorrent set it
-            # settings["listen_interfaces"] = "0.0.0.0:%d" % anon_port
+            # settings["listen_interfaces"] = f"0.0.0.0:{anon_port}"
 
             # By default block all IPs except 1.1.1.1 (which is used to ensure libtorrent makes a connection to us)
             self.update_ip_filter(ltsession, ['1.1.1.1'])
@@ -363,7 +363,8 @@ def set_max_connections(self, conns, hops=None):
     def set_upload_rate_limit(self, rate, hops=None):
         # Rate conversion due to the fact that we had a different system with Swift
         # and the old python BitTorrent core: unlimited == 0, stop == -1, else rate in kbytes
-        libtorrent_rate = int(-1 if rate == 0 else (1 if rate == -1 else rate * 1024))
+        torrent_rate = {0: -1, -1: 1}
+        libtorrent_rate = torrent_rate.get(rate, rate * 1024)
 
         # Pass outgoing_port and num_outgoing_ports to dict due to bug in libtorrent 0.16.18
         settings_dict = {'upload_rate_limit': libtorrent_rate, 'outgoing_port': 0, 'num_outgoing_ports': 1}
@@ -374,10 +375,12 @@ def get_upload_rate_limit(self, hops=None):
         # Rate conversion due to the fact that we had a different system with Swift
         # and the old python BitTorrent core: unlimited == 0, stop == -1, else rate in kbytes
         libtorrent_rate = self.get_session(hops).upload_rate_limit()
-        return 0 if libtorrent_rate == -1 else (-1 if libtorrent_rate == 1 else libtorrent_rate / 1024)
+        torrent_rate = {-1: 0, 1: -1}
+        return torrent_rate.get(libtorrent_rate, libtorrent_rate // 1024)
 
     def set_download_rate_limit(self, rate, hops=None):
-        libtorrent_rate = int(-1 if rate == 0 else (1 if rate == -1 else rate * 1024))
+        torrent_rate = {0: -1, -1: 1}
+        libtorrent_rate = torrent_rate.get(rate, rate * 1024)
 
         # Pass outgoing_port and num_outgoing_ports to dict due to bug in libtorrent 0.16.18
         settings_dict = {'download_rate_limit': libtorrent_rate}
@@ -386,7 +389,8 @@ def set_download_rate_limit(self, rate, hops=None):
 
     def get_download_rate_limit(self, hops=0):
         libtorrent_rate = self.get_session(hops).download_rate_limit()
-        return 0 if libtorrent_rate == -1 else (-1 if libtorrent_rate == 1 else libtorrent_rate / 1024)
+        torrent_rate = {-1: 0, 1: -1}
+        return torrent_rate.get(libtorrent_rate, libtorrent_rate // 1024)
 
     def process_alert(self, alert, hops=0):
         alert_type = alert.__class__.__name__
@@ -780,7 +784,7 @@ def update_trackers(self, infohash, trackers):
             old_def = download.get_def()
             old_trackers = old_def.get_trackers()
             new_trackers = list(set(trackers) - old_trackers)
-            all_trackers = list(old_trackers) + new_trackers
+            all_trackers = [*old_trackers, *new_trackers]
 
             if new_trackers:
                 # Add new trackers to the download
diff --git a/src/tribler/core/components/libtorrent/tests/test_download_manager.py b/src/tribler/core/components/libtorrent/tests/test_download_manager.py
index 2834c5668f6..59be9560ba7 100644
--- a/src/tribler/core/components/libtorrent/tests/test_download_manager.py
+++ b/src/tribler/core/components/libtorrent/tests/test_download_manager.py
@@ -1,4 +1,5 @@
 import asyncio
+import functools
 from asyncio import Future, gather, get_event_loop, sleep
 from unittest.mock import MagicMock
 
@@ -27,9 +28,10 @@ def create_fake_download_and_state():
     fake_download.get_def().get_name_as_unicode = lambda: "test.iso"
     fake_download.get_peerlist = lambda: [fake_peer]
     fake_download.hidden = False
-    fake_download.checkpoint = lambda: succeed(None)
-    fake_download.stop = lambda: succeed(None)
-    fake_download.shutdown = lambda: succeed(None)
+    succeed_none = functools.partial(succeed, None)
+    fake_download.checkpoint = succeed_none
+    fake_download.stop = succeed_none
+    fake_download.shutdown = succeed_none
     dl_state = MagicMock()
     dl_state.get_infohash = lambda: b'aaaa'
     dl_state.get_status = lambda: DownloadStatus.SEEDING
@@ -138,9 +140,10 @@ async def test_get_metainfo_with_already_added_torrent(fake_dlmgr):
 
     download_impl = MagicMock()
     download_impl.future_metainfo = succeed(bencode(torrent_def.get_metainfo()))
-    download_impl.checkpoint = lambda: succeed(None)
-    download_impl.stop = lambda: succeed(None)
-    download_impl.shutdown = lambda: succeed(None)
+    succeed_none = functools.partial(succeed, None)
+    download_impl.checkpoint = succeed_none
+    download_impl.stop = succeed_none
+    download_impl.shutdown = succeed_none
 
     fake_dlmgr.initialize()
     fake_dlmgr.downloads[torrent_def.infohash] = download_impl
@@ -155,10 +158,10 @@ async def test_start_download_while_getting_metainfo(fake_dlmgr):
     infohash = b"a" * 20
 
     metainfo_session = MagicMock()
-    metainfo_session.get_torrents = lambda: []
+    metainfo_session.get_torrents = list
 
     metainfo_dl = MagicMock()
-    metainfo_dl.get_def = lambda: MagicMock(get_infohash=lambda: infohash)
+    metainfo_dl.get_def = functools.partial(MagicMock, get_infohash=lambda: infohash)
 
     fake_dlmgr.initialize()
     fake_dlmgr.get_session = lambda *_: metainfo_session
@@ -181,7 +184,7 @@ async def test_start_download(fake_dlmgr):
     infohash = b'a' * 20
 
     mock_handle = MagicMock()
-    mock_handle.info_hash = lambda: hexlify(infohash)
+    mock_handle.info_hash = functools.partial(hexlify, infohash)
     mock_handle.is_valid = lambda: True
 
     mock_error = MagicMock()
@@ -192,7 +195,7 @@ async def test_start_download(fake_dlmgr):
                                                            category=lambda _: None))()
 
     mock_ltsession = MagicMock()
-    mock_ltsession.get_torrents = lambda: []
+    mock_ltsession.get_torrents = list
     mock_ltsession.async_add_torrent = lambda _: fake_dlmgr.register_task('post_alert',
                                                                           fake_dlmgr.process_alert,
                                                                           mock_alert, delay=0.1)
@@ -241,7 +244,7 @@ async def test_start_download_existing_handle(fake_dlmgr):
     infohash = b'a' * 20
 
     mock_handle = MagicMock()
-    mock_handle.info_hash = lambda: hexlify(infohash)
+    mock_handle.info_hash = functools.partial(hexlify, infohash)
     mock_handle.is_valid = lambda: True
 
     mock_ltsession = MagicMock()
@@ -319,7 +322,7 @@ def on_set_settings(settings):
         assert settings['proxy_hostnames']
 
     mock_lt_session = MagicMock()
-    mock_lt_session.get_settings = lambda: {}
+    mock_lt_session.get_settings = dict
     mock_lt_session.set_settings = on_set_settings
     mock_lt_session.set_proxy = on_proxy_set  # Libtorrent < 1.1.0 uses set_proxy to set proxy settings
     fake_dlmgr.set_proxy_settings(mock_lt_session, 0, ('a', "1234"), ('abc', 'def'))
@@ -406,7 +409,7 @@ def mocked_load_checkpoint(filename):
         mocked_load_checkpoint.called = True
 
     mocked_load_checkpoint.called = False
-    fake_dlmgr.get_checkpoint_dir = lambda: Path(tmpdir)
+    fake_dlmgr.get_checkpoint_dir = functools.partial(Path, tmpdir)
 
     with open(fake_dlmgr.get_checkpoint_dir() / 'abcd.conf', 'wb') as state_file:
         state_file.write(b"hi")
diff --git a/src/tribler/core/components/libtorrent/torrentdef.py b/src/tribler/core/components/libtorrent/torrentdef.py
index 952792bc1db..90013c876c2 100644
--- a/src/tribler/core/components/libtorrent/torrentdef.py
+++ b/src/tribler/core/components/libtorrent/torrentdef.py
@@ -35,7 +35,7 @@ def escape_as_utf8(string, encoding='utf8'):
             # latin1 and hope for the best (minor corruption).
             return string.decode('latin1').encode('utf8', 'ignore').decode('utf8')
         except (TypeError, ValueError):
-            # This is a very nasty string (e.g. u'\u266b'), remove the illegal entries.
+            # This is a very nasty string (e.g. '\u266b'), remove the illegal entries.
             return string.encode('utf8', 'ignore').decode('utf8')
 
 
diff --git a/src/tribler/core/components/metadata_store/restapi/search_endpoint.py b/src/tribler/core/components/metadata_store/restapi/search_endpoint.py
index dfbaef20d45..c992009af3d 100644
--- a/src/tribler/core/components/metadata_store/restapi/search_endpoint.py
+++ b/src/tribler/core/components/metadata_store/restapi/search_endpoint.py
@@ -1,3 +1,4 @@
+import operator
 import time
 from collections import defaultdict
 from typing import Dict, List
@@ -57,7 +58,7 @@ def build_snippets(self, search_results: List[Dict]) -> List[Dict]:
 
         # Sort the search results within each snippet by the number of seeders
         for torrents_list in content_to_torrents.values():
-            torrents_list.sort(key=lambda x: x["num_seeders"], reverse=True)
+            torrents_list.sort(key=operator.itemgetter("num_seeders"), reverse=True)
 
         # Determine the most popular content items - this is the one we show
         sorted_content_info = list(content_to_torrents.items())
diff --git a/src/tribler/core/components/reporter/reported_error.py b/src/tribler/core/components/reporter/reported_error.py
index 3968f8c0aff..f0c449409f4 100644
--- a/src/tribler/core/components/reporter/reported_error.py
+++ b/src/tribler/core/components/reporter/reported_error.py
@@ -7,7 +7,7 @@ class ReportedError:
     type: str
     text: str
     event: dict = field(repr=False)
-    additional_information: dict = field(default_factory=lambda: {}, repr=False)
+    additional_information: dict = field(default_factory=dict, repr=False)
 
     long_text: str = field(default='', repr=False)
     context: str = field(default='', repr=False)
diff --git a/src/tribler/core/components/tunnel/community/dispatcher.py b/src/tribler/core/components/tunnel/community/dispatcher.py
index d7a3b2cb135..244aeacbe53 100644
--- a/src/tribler/core/components/tunnel/community/dispatcher.py
+++ b/src/tribler/core/components/tunnel/community/dispatcher.py
@@ -1,3 +1,4 @@
+import functools
 import random
 from collections import defaultdict
 
@@ -97,6 +98,11 @@ async def on_socks5_tcp_data(self, tcp_connection, destination, request):
             tcp_connection.transport.write(response)
         tcp_connection.transport.close()
 
+    def _add_data_if_result(self, result_func, connection, request):
+        if not result_func.result():
+            return None
+        return self.on_socks5_udp_data(connection, request)
+
     def select_circuit(self, connection, request):
         if request.destination[1] == CIRCUIT_ID_PORT:
             circuit = self.tunnels.circuits.get(self.tunnels.ip_to_circuit_id(request.destination[0]))
@@ -120,8 +126,13 @@ def select_circuit(self, connection, request):
                 return None
             self._logger.debug("Creating circuit for data to %s. Retrying later..", request.destination)
             self.cid_to_con[circuit.circuit_id] = connection
-            circuit.ready.add_done_callback(lambda f, c=connection.udp_connection, r=request:
-                                            self.on_socks5_udp_data(c, r) if f.result() else None)
+            circuit.ready.add_done_callback(
+                functools.partial(
+                    self._add_data_if_result,
+                    connection=connection.udp_connection,
+                    request=request
+                )
+            )
             return None
 
         circuit = random.choice(options)
diff --git a/src/tribler/core/components/tunnel/community/tunnel_community.py b/src/tribler/core/components/tunnel/community/tunnel_community.py
index c9896ec31fa..9b0aa0fe111 100644
--- a/src/tribler/core/components/tunnel/community/tunnel_community.py
+++ b/src/tribler/core/components/tunnel/community/tunnel_community.py
@@ -1,3 +1,4 @@
+import functools
 import hashlib
 import math
 import sys
@@ -503,7 +504,7 @@ def monitor_downloads(self, dslist):
             if state_changed and new_state in active:
                 if old_state != DownloadStatus.METADATA or new_state != DownloadStatus.DOWNLOADING:
                     self.join_swarm(info_hash, hops[info_hash], seeding=new_state == DownloadStatus.SEEDING,
-                                    callback=lambda addr, ih=info_hash: self.on_e2e_finished(addr, ih))
+                                    callback=functools.partial(self.on_e2e_finished, info_hash=info_hash))
             elif state_changed and new_state in [DownloadStatus.STOPPED, None]:
                 self.leave_swarm(info_hash)
 
diff --git a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388a67997fd4.state b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388a67997fd4.state
index 3bc90e77e0d..25a62fa1ed0 100644
--- a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388a67997fd4.state
+++ b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388a67997fd4.state
@@ -14,4 +14,4 @@ channel_download = True
 version = 5
 metainfo = {'creation date': 1562337604, 'info': {'files': [{'path': ['1562337581003.mdblob.lz4'], 'length': 295}], 'piece length': 16384, 'name': '5263ec553e7a062ac4f75eb6f7bf26f7400b800d74b575f6', 'pieces': '\x17\x18u\xcd\xae\xa2\xc9f*g3\x13u\xda{c\xab\xbc\xae\xc8'}}
 dlstate = {'status': 1, 'progress': 0, 'swarmcache': None}
-engineresumedata = {'active_time': 0, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'paused': 0, 'seeding_time': 0, 'info-hash': '>\xfb~\x91W\x11\x0e\x1a%\x9d: t\x038\x8ag\x99\x7f\xd4', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'unfinished': [], 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337604, 'banned_peers6': '', 'file_priority': [1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': u'channels', 'peers': '', 'completed_time': 0, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 0, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0}
+engineresumedata = {'active_time': 0, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'paused': 0, 'seeding_time': 0, 'info-hash': '>\xfb~\x91W\x11\x0e\x1a%\x9d: t\x038\x8ag\x99\x7f\xd4', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'unfinished': [], 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337604, 'banned_peers6': '', 'file_priority': [1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': 'channels', 'peers': '', 'completed_time': 0, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 0, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0}
diff --git a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388fffffffff.state b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388fffffffff.state
index a163cd17558..40940222b25 100644
--- a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388fffffffff.state
+++ b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/3efb7e9157110e1a259d3a207403388fffffffff.state
@@ -14,4 +14,4 @@ channel_download = True
 version = 5
 metainfo = {'creation date': 1562337604, 'info': {'files': [{'path': ['1562337581003.mdblob.lz4'], 'length': 295}], 'piece length': 16384, 'name': '5263ec553e7a062ac4f75eb6f7bf26f7400b800d74b575f6', 'pieces': '\x17\x18u\xcd\xae\xa2\xc9f*g3\x13u\xda{c\xab\xbc\xae\xc8'}}
 dlstate = {'status': 1, 'progress': 0, 'swarmcache': None}
-engineresumedata = {'active_time': 0, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'paused': 0, 'seeding_time': 0, 'info-hash': '>\xfb~\x91W\x11\x0e\x1a%\x9d: t\x038\x8ag\x99\x7f\xd4', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'unfinished': [], 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337604, 'banned_peers6': '', 'file_priority': [1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': u'channels', 'peers': '', 'completed_time': 0, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 0, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0}
+engineresumedata = {'active_time': 0, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'paused': 0, 'seeding_time': 0, 'info-hash': '>\xfb~\x91W\x11\x0e\x1a%\x9d: t\x038\x8ag\x99\x7f\xd4', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'unfinished': [], 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337604, 'banned_peers6': '', 'file_priority': [1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': 'channels', 'peers': '', 'completed_time': 0, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 0, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0}
diff --git a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/811c1c033474e6a07e42f3f90f3f31dcad7dccc1.state b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/811c1c033474e6a07e42f3f90f3f31dcad7dccc1.state
index bfb4784de27..eb3f9470660 100644
--- a/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/811c1c033474e6a07e42f3f90f3f31dcad7dccc1.state
+++ b/src/tribler/core/tests/tools/data/noncompliant_state_dir/dlcheckpoints/811c1c033474e6a07e42f3f90f3f31dcad7dccc1.state
@@ -14,4 +14,4 @@ channel_download = True
 version = 5
 metainfo = {'creation date': 1562337893, 'info': {'files': [{'path': ['1562337481003.mdblob.lz4'], 'length': 306}, {'path': ['1562337581005.mdblob.lz4'], 'length': 270}], 'piece length': 16384, 'name': '5263ec553e7a062ac4f75eb6f7bf26f7', 'pieces': '\xc7\xd7\xdf\xcf/x$D\xd3UQ\xcc\x90\x13\xa2\x1c\x82c\x13Y'}}
 dlstate = {'status': 4, 'progress': 1.0, 'swarmcache': None}
-engineresumedata = {'active_time': 10, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'pieces': '\x01', 'paused': 0, 'seeding_time': 10, 'info-hash': '\x81\x1c\x1c\x034t\xe6\xa0~B\xf3\xf9\x0f?1\xdc\xad}\xcc\xc1', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337893, 'banned_peers6': '', 'file_priority': [1, 1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': u'channels', 'peers': '', 'completed_time': 1562337894, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 10, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0, 'file sizes': [[306, 1562337511], [270, 1562337893]]}
+engineresumedata = {'active_time': 10, 'num_incomplete': 16777215, 'announce_to_lsd': 1, 'seed_mode': 0, 'pieces': '\x01', 'paused': 0, 'seeding_time': 10, 'info-hash': '\x81\x1c\x1c\x034t\xe6\xa0~B\xf3\xf9\x0f?1\xdc\xad}\xcc\xc1', 'upload_rate_limit': -1, 'max_uploads': 16777215, 'max_connections': 16777215, 'num_downloaded': 16777215, 'total_downloaded': 0, 'file-format': 'libtorrent resume file', 'peers6': '', 'added_time': 1562337893, 'banned_peers6': '', 'file_priority': [1, 1], 'last_seen_complete': 0, 'total_uploaded': 0, 'file-version': 1, 'auto_managed': 0, 'save_path': 'channels', 'peers': '', 'completed_time': 1562337894, 'blocks per piece': 1, 'download_rate_limit': -1, 'libtorrent-version': '1.1.5.0', 'banned_peers': '', 'sequential_download': 0, 'announce_to_trackers': 1, 'num_complete': 16777215, 'finished_time': 10, 'announce_to_dht': 1, 'trackers': [[]], 'super_seeding': 0, 'file sizes': [[306, 1562337511], [270, 1562337893]]}
diff --git a/src/tribler/gui/dialogs/feedbackdialog.py b/src/tribler/gui/dialogs/feedbackdialog.py
index 767810695df..ef8549b8fd3 100644
--- a/src/tribler/gui/dialogs/feedbackdialog.py
+++ b/src/tribler/gui/dialogs/feedbackdialog.py
@@ -129,8 +129,7 @@ def on_cancel_clicked(self, checked):
     def on_send_clicked(self, checked):
         self.send_report_button.setEnabled(False)
         self.send_report_button.setText(tr("SENDING..."))
-
-        sys_info = defaultdict(lambda: [])
+        sys_info = defaultdict(list)
         for ind in range(self.env_variables_list.topLevelItemCount()):
             item = self.env_variables_list.topLevelItem(ind)
             key = item.text(0)
diff --git a/src/tribler/gui/utilities.py b/src/tribler/gui/utilities.py
index e9c2e1d7af7..0d79997b5c2 100644
--- a/src/tribler/gui/utilities.py
+++ b/src/tribler/gui/utilities.py
@@ -72,7 +72,7 @@ def tr(key):
 
 
 def data_item2uri(data_item):
-    return f"magnet:?xt=urn:btih:{data_item[u'infohash']}&dn={data_item[u'name']}"
+    return f"magnet:?xt=urn:btih:{data_item['infohash']}&dn={data_item['name']}"
 
 
 def index2uri(index):
diff --git a/src/tribler/gui/widgets/downloadsdetailstabwidget.py b/src/tribler/gui/widgets/downloadsdetailstabwidget.py
index 702fd2b4362..29cbd398725 100644
--- a/src/tribler/gui/widgets/downloadsdetailstabwidget.py
+++ b/src/tribler/gui/widgets/downloadsdetailstabwidget.py
@@ -1,3 +1,4 @@
+import operator
 from enum import IntEnum
 from pathlib import PurePosixPath
 from typing import Dict, Optional
@@ -27,7 +28,7 @@ class DownloadDetailsTabs(IntEnum):
 def convert_to_files_tree_format(download_info):
     files = download_info['files']
     out = []
-    for file in sorted(files, key=lambda x: x['index']):
+    for file in sorted(files, key=operator.itemgetter("index")):
         file_path_parts = PurePosixPath(file['name']).parts
         file_path = [download_info['name'], *file_path_parts]
         if len(files) == 1:
diff --git a/src/tribler/gui/widgets/graphs/timeseriesplot.py b/src/tribler/gui/widgets/graphs/timeseriesplot.py
index 4bbc563dc73..a907e3d2153 100644
--- a/src/tribler/gui/widgets/graphs/timeseriesplot.py
+++ b/src/tribler/gui/widgets/graphs/timeseriesplot.py
@@ -1,3 +1,4 @@
+import operator
 import time
 
 import numpy as np
@@ -45,7 +46,7 @@ def add_data(self, timestamp, data):
 
     def render_plot(self):
         # Sort the plot data before rendering via plot.setData() to prevent loops and extra lines in the graph.
-        self.plot_data = dict(sorted(self.plot_data.items(), key=lambda x: x[0]))
+        self.plot_data = dict(sorted(self.plot_data.items(), key=operator.itemgetter(0)))
 
         for i, plot in enumerate(self.plots):
             plot.setData(