diff --git a/ditto/core/apps.py b/ditto/core/apps.py
index 82f119a..22e03a3 100644
--- a/ditto/core/apps.py
+++ b/ditto/core/apps.py
@@ -38,7 +38,7 @@ def enabled(self):
 
     def is_installed(self, app_name):
         "Is this Ditto app installed?"
-        return apps.is_installed("ditto.%s" % app_name)
+        return apps.is_installed(f"ditto.{app_name}")
 
     def is_enabled(self, app_name):
         """Determine if a particular Ditto app is installed and enabled.
@@ -52,7 +52,7 @@ def is_enabled(self, app_name):
         Doesn't offer much over apps.is_installed() yet, but would let us add other
         conditions in future, like being able to enable/disable installed apps.
         """
-        return apps.is_installed("ditto.%s" % app_name)
+        return apps.is_installed(f"ditto.{app_name}")
 
 
 ditto_apps = Apps()
diff --git a/ditto/core/management/commands/__init__.py b/ditto/core/management/commands/__init__.py
index 6280c90..7232295 100644
--- a/ditto/core/management/commands/__init__.py
+++ b/ditto/core/management/commands/__init__.py
@@ -40,7 +40,7 @@ def output_results(self, results, verbosity=1):
             return
 
         for result in results:
-            prefix = "%s: " % result["account"] if "account" in result else ""
+            prefix = f"{result['account']}: " if "account" in result else ""
             if "fetched" in result:
                 noun = (
                     self.singular_noun if result["fetched"] == 1 else self.plural_noun
diff --git a/ditto/core/templatetags/ditto_core.py b/ditto/core/templatetags/ditto_core.py
index cb18eae..3bff640 100644
--- a/ditto/core/templatetags/ditto_core.py
+++ b/ditto/core/templatetags/ditto_core.py
@@ -88,19 +88,18 @@ def display_time(dt, *, link_to_day=False, granularity=0, case=None):
     """
 
     if granularity == 8:
-        visible_time = "circa %s" % dt.strftime(app_settings.CORE_DATE_YEAR_FORMAT)
+        year = dt.strftime(app_settings.CORE_DATE_YEAR_FORMAT)
+        visible_time = f"circa {year}"
         stamp = dt.strftime("%Y")
 
     elif granularity == 6:
-        visible_time = "sometime in %s" % dt.strftime(
-            app_settings.CORE_DATE_YEAR_FORMAT
-        )
+        year = dt.strftime(app_settings.CORE_DATE_YEAR_FORMAT)
+        visible_time = f"sometime in {year}"
         stamp = dt.strftime("%Y")
 
     elif granularity == 4:
-        visible_time = "sometime in %s" % dt.strftime(
-            app_settings.CORE_DATE_YEAR_MONTH_FORMAT
-        )
+        year_month = dt.strftime(app_settings.CORE_DATE_YEAR_MONTH_FORMAT)
+        visible_time = f"sometime in {year_month}"
         stamp = dt.strftime("%Y-%m")
 
     else:
diff --git a/ditto/core/views.py b/ditto/core/views.py
index 7dd6a03..2d841c9 100644
--- a/ditto/core/views.py
+++ b/ditto/core/views.py
@@ -246,7 +246,8 @@ def set_app_and_variety(self, **kwargs):
                 )
                 raise Http404(msg)
         elif app_slug:
-            raise Http404("'%s' is not a valid app slug." % app_slug)
+            msg = f"'{app_slug}' is not a valid app slug."
+            raise Http404(msg)
 
         self.app_slug = app_slug
         self.variety_slug = variety_slug
@@ -558,7 +559,10 @@ def get_variety_counts(self):
             date_field = self.get_date_field_for_app_variety(app_name, variety_name)
             qs = self.get_queryset_for_app_variety(app_name, variety_name)
             qs = qs.filter(
-                **{"%s__gte" % date_field: since, "%s__lt" % date_field: until}
+                **{
+                    f"{date_field}__gte": since,
+                    f"{date_field}__lt": until,
+                }
             )
             paginate_by = self.get_paginate_by(qs)
             # if not allow_future:
diff --git a/ditto/flickr/admin.py b/ditto/flickr/admin.py
index 12a3fc2..1245b7c 100644
--- a/ditto/flickr/admin.py
+++ b/ditto/flickr/admin.py
@@ -133,9 +133,7 @@ class UserAdmin(admin.ModelAdmin):
     )
 
     def show_avatar(self, instance):
-        return mark_safe(
-            '<img src="%s" width="24" height="24" />' % (instance.avatar_url)
-        )
+        return mark_safe(f'<img src="{instance.avatar_url}" width="24" height="24" />')
 
     show_avatar.short_description = ""
 
diff --git a/ditto/flickr/fetch/fetchers.py b/ditto/flickr/fetch/fetchers.py
index 1c0e6e6..27beb4b 100644
--- a/ditto/flickr/fetch/fetchers.py
+++ b/ditto/flickr/fetch/fetchers.py
@@ -74,7 +74,7 @@ def __init__(self, account):
             if account.user:
                 self.return_value["account"] = account.user.username
             elif account.pk:
-                self.return_value["account"] = "Account: %s" % str(account)
+                self.return_value["account"] = f"Account: {account}"
             else:
                 self.return_value["account"] = "Unsaved Account"
         else:
@@ -115,14 +115,14 @@ def _fetch_page(self, **kwargs):
             self._call_api(**kwargs)
         except FetchError as e:
             self.return_value["success"] = False
-            self.return_value["messages"] = ["Error when calling Flickr API: %s" % e]
+            self.return_value["messages"] = [f"Error when calling Flickr API: {e}"]
             return
 
         try:
             self._fetch_extra()
         except FetchError as e:
             self.return_value["success"] = False
-            self.return_value["messages"] = ["Error when fetching extra data: %s" % e]
+            self.return_value["messages"] = [f"Error when fetching extra data: {e}"]
             return
 
         try:
@@ -131,7 +131,7 @@ def _fetch_page(self, **kwargs):
             self.results = []
         except FetchError as e:
             self.return_value["success"] = False
-            self.return_value["messages"] = ["Error when saving data: %s" % e]
+            self.return_value["messages"] = [f"Error when saving data: {e}"]
             return
 
         return
diff --git a/ditto/flickr/management/commands/fetch_flickr_account_user.py b/ditto/flickr/management/commands/fetch_flickr_account_user.py
index b0b9572..78bb637 100644
--- a/ditto/flickr/management/commands/fetch_flickr_account_user.py
+++ b/ditto/flickr/management/commands/fetch_flickr_account_user.py
@@ -33,7 +33,7 @@ def handle(self, *args, **options):
         try:
             account = Account.objects.get(id=options["id"])
         except Account.DoesNotExist:
-            self.stderr.write("No Account found with an id of '%s'" % options["id"])
+            self.stderr.write(f"No Account found with an id of '{options['id']}'")
 
         if account:
             # Then get the ID of the Flicker user for this Account's API creds.
@@ -53,7 +53,7 @@ def handle(self, *args, **options):
                     account.save()
                     if options.get("verbosity", 1) > 0:
                         self.stdout.write(
-                            "Fetched and saved user '%s'" % result["user"]["name"]
+                            f"Fetched and saved user '{result['user']['name']}'"
                         )
                 else:
                     if options.get("verbosity", 1) > 0:
@@ -65,6 +65,6 @@ def handle(self, *args, **options):
             else:
                 if options.get("verbosity", 1) > 0:
                     self.stderr.write(
-                        "Failed to fetch a Flickr ID for this Account: %s"
-                        % id_result["messages"][0]
+                        "Failed to fetch a Flickr ID for this Account: "
+                        f"{id_result["messages"][0]}"
                     )
diff --git a/ditto/flickr/templatetags/ditto_flickr.py b/ditto/flickr/templatetags/ditto_flickr.py
index 64501f2..4890a98 100644
--- a/ditto/flickr/templatetags/ditto_flickr.py
+++ b/ditto/flickr/templatetags/ditto_flickr.py
@@ -40,9 +40,8 @@ def day_photos(date, nsid=None, time="post_time"):
     time -- A string, either 'post_time' (default) or 'taken_time'.
     """
     if time not in ["post_time", "taken_time"]:
-        raise ValueError(
-            "`time` must be either 'post_time' or " "'taken_time', not '%s'." % time
-        )
+        msg = f"`time` must be either 'post_time' or 'taken_time', not '{time}'."
+        raise ValueError(msg)
 
     start = datetime.combine(date, datetime_time.min).replace(tzinfo=timezone.utc)
     end = datetime.combine(date, datetime_time.max).replace(tzinfo=timezone.utc)
@@ -107,10 +106,10 @@ def annual_photo_counts(nsid=None, count_by="post_time"):
     """
 
     if count_by not in ["post_time", "taken_time"]:
-        raise ValueError(
-            "`count_by` must be either 'post_time' or "
-            "'taken_time', not '%s'." % count_by
+        msg = (
+            f"`count_by` must be either 'post_time' or 'taken_time', not '{count_by}'."
         )
+        raise ValueError(msg)
 
     qs = Photo.public_photo_objects
 
diff --git a/ditto/lastfm/fetch.py b/ditto/lastfm/fetch.py
index 526062a..e9c81e5 100644
--- a/ditto/lastfm/fetch.py
+++ b/ditto/lastfm/fetch.py
@@ -81,16 +81,15 @@ def fetch(self, fetch_type="recent", days=None):
         if self.account and self.account.is_active is False:
             self.return_value["success"] = False
             self.return_value["messages"] = [
-                "The Account %s is currently marked as inactive."
-                % self.account.username
+                f"The Account {self.account.username} is currently marked as inactive."
             ]
             return self.return_value
 
         valid_fetch_types = ["all", "days", "recent"]
         if fetch_type not in valid_fetch_types:
-            raise ValueError(
-                "fetch_type should be one of %s" % ", ".join(valid_fetch_types)
-            )
+            types_str = ", ".join(valid_fetch_types)
+            msg = f"fetch_type should be one of {types_str}"
+            raise ValueError(msg)
 
         if fetch_type == "days":
             try:
diff --git a/ditto/lastfm/managers.py b/ditto/lastfm/managers.py
index 70a80e9..b3f23bb 100644
--- a/ditto/lastfm/managers.py
+++ b/ditto/lastfm/managers.py
@@ -79,31 +79,30 @@ def with_scrobble_counts(self, **kwargs):
             raise ValueError(msg)
 
         if account is not None and account.__class__.__name__ != "Account":
-            raise TypeError(
-                "account must be an Account instance, " "not a %s" % type(account)
-            )
+            msg = f"account must be an Account instance, not a {type(account)}"
+            raise TypeError(msg)
 
         if album is not None and album.__class__.__name__ != "Album":
-            raise TypeError(
-                "album must be an Album instance, " "not a %s" % type(album)
-            )
+            msg = f"album must be an Album instance, not a {type(album)}"
+            raise TypeError(msg)
 
         if artist is not None and artist.__class__.__name__ != "Artist":
-            raise TypeError(
-                "artist must be an Artist instance, " "not a %s" % type(account)
-            )
+            msg = f"artist must be an Artist instance, not a {type(account)}"
+            raise TypeError(msg)
 
         if min_post_time is not None and type(min_post_time) is not datetime:
-            raise TypeError(
+            msg = (
                 "min_post_time must be a datetime.datetime, "
-                "not a %s" % type(min_post_time)
+                f"not a {type(min_post_time)}"
             )
+            raise TypeError(msg)
 
         if max_post_time is not None and type(max_post_time) is not datetime:
-            raise TypeError(
+            msg = (
                 "max_post_time must be a datetime.datetime, "
-                "not a %s" % type(max_post_time)
+                f"not a {type(max_post_time)}"
             )
+            raise TypeError(msg)
 
         filter_kwargs = {}
 
diff --git a/ditto/lastfm/templatetags/ditto_lastfm.py b/ditto/lastfm/templatetags/ditto_lastfm.py
index 8090b57..8073079 100644
--- a/ditto/lastfm/templatetags/ditto_lastfm.py
+++ b/ditto/lastfm/templatetags/ditto_lastfm.py
@@ -22,9 +22,8 @@ def check_top_kwargs(**kwargs):
     period = kwargs["period"]
 
     if account is not None and not isinstance(account, Account):
-        raise TypeError(
-            "`account` must be an Account instance, " "not a %s" % type(account)
-        )
+        msg = f"`account` must be an Account instance, not a {type(account)}"
+        raise TypeError(msg)
 
     if limit != "all" and isinstance(limit, int) is False:
         msg = "`limit` must be an integer or 'all'"
@@ -35,13 +34,15 @@ def check_top_kwargs(**kwargs):
         and not isinstance(date, datetime.datetime)
         and not isinstance(date, datetime.date)
     ):
-        raise TypeError("`date` must be a datetime or date, " "not a %s" % type(date))
+        msg = f"`date` must be a datetime or date, not a {type(date)}"
+        raise TypeError(msg)
 
     if period not in ["day", "week", "month", "year"]:
-        raise TypeError(
+        msg = (
             '`period` must be one of "day", "week", "month" or "year", '
-            "not %s" % type(period)
+            f"not {type(period)}"
         )
+        raise TypeError(msg)
 
 
 def get_period_times(date, period):
@@ -120,7 +121,8 @@ def top_albums(account=None, artist=None, limit=10, date=None, period="day"):
     check_top_kwargs(account=account, limit=limit, date=date, period=period)
 
     if artist is not None and not isinstance(artist, Artist):
-        raise TypeError("artist must be an Artist instance, " "not a %s" % type(artist))
+        msg = f"artist must be an Artist instance, not a {type(artist)}"
+        raise TypeError(msg)
 
     qs_kwargs = {}
 
@@ -208,10 +210,12 @@ def top_tracks(
     check_top_kwargs(account=account, limit=limit, date=date, period=period)
 
     if album is not None and type(album) is not Album:
-        raise TypeError("album must be an Album instance, " "not a %s" % type(album))
+        msg = f"album must be an Album instance, not a {type(album)}"
+        raise TypeError(msg)
 
     if artist is not None and type(artist) is not Artist:
-        raise TypeError("artist must be an Artist instance, " "not a %s" % type(artist))
+        msg = f"artist must be an Artist instance, not a {type(artist)}"
+        raise TypeError(msg)
 
     qs_kwargs = {}
 
@@ -247,9 +251,8 @@ def recent_scrobbles(account=None, limit=10):
     limit -- Maximum number to fetch. Default is 10.
     """
     if account is not None and not isinstance(account, Account):
-        raise TypeError(
-            "account must be an Account instance, " "not a %s" % type(account)
-        )
+        msg = f"account must be an Account instance, not a {type(account)}"
+        raise TypeError(msg)
 
     if isinstance(limit, int) is False:
         msg = "`limit` must be an integer"
@@ -279,12 +282,12 @@ def day_scrobbles(date, account=None):
     account -- An Account object or None (default, Scrobbles by all Accounts).
     """
     if not isinstance(date, datetime.datetime) and not isinstance(date, datetime.date):
-        raise TypeError("date must be a datetime or date, " "not a %s" % type(date))
+        msg = f"date must be a datetime or date, not a {type(date)}"
+        raise TypeError(msg)
 
     if account is not None and not isinstance(account, Account):
-        raise TypeError(
-            "account must be an Account instance, " "not a %s" % type(account)
-        )
+        msg = f"account must be an Account instance, not a {type(account)}"
+        raise TypeError(msg)
 
     qs_kwargs = {}
 
@@ -322,9 +325,8 @@ def annual_scrobble_counts(account=None):
     """
 
     if account is not None and not isinstance(account, Account):
-        raise TypeError(
-            "account must be an Account instance, " "not a %s" % type(account)
-        )
+        msg = f"account must be an Account instance, not a {type(account)}"
+        raise TypeError(msg)
 
     qs = Scrobble.objects
 
diff --git a/ditto/lastfm/urls.py b/ditto/lastfm/urls.py
index 079b868..a9e31cf 100644
--- a/ditto/lastfm/urls.py
+++ b/ditto/lastfm/urls.py
@@ -28,12 +28,12 @@
         name="track_list",
     ),
     re_path(
-        r"^music/(?P<artist_slug>%s)/$" % slug_chars,
+        rf"^music/(?P<artist_slug>{slug_chars})/$",
         view=views.ArtistDetailView.as_view(),
         name="artist_detail",
     ),
     re_path(
-        r"^music/(?P<artist_slug>%s)/\+albums/$" % slug_chars,
+        rf"^music/(?P<artist_slug>{slug_chars})/\+albums/$",
         view=views.ArtistAlbumsView.as_view(),
         name="artist_albums",
     ),
diff --git a/ditto/pinboard/factories.py b/ditto/pinboard/factories.py
index f1abfc8..d3d526e 100644
--- a/ditto/pinboard/factories.py
+++ b/ditto/pinboard/factories.py
@@ -12,8 +12,8 @@ class Meta:
         model = models.Account
 
     username = factory.Sequence(lambda n: "user%d" % n)
-    url = factory.LazyAttribute(lambda obj: "https://pinboard.com/%s" % obj.username)
-    api_token = factory.LazyAttribute(lambda obj: "%s:123ABC" % obj.username)
+    url = factory.LazyAttribute(lambda obj: f"https://pinboard.com/{obj.username}")
+    api_token = factory.LazyAttribute(lambda obj: f"{obj.username}:123ABC")
 
 
 class BookmarkFactory(factory.django.DjangoModelFactory):
diff --git a/ditto/pinboard/fetch.py b/ditto/pinboard/fetch.py
index dce9d16..34845aa 100644
--- a/ditto/pinboard/fetch.py
+++ b/ditto/pinboard/fetch.py
@@ -85,9 +85,8 @@ def _get_accounts(self, username):
             if account.is_active:
                 accounts = [account]
             else:
-                raise FetchError(
-                    "The account %s is curently marked as inactive." % username
-                )
+                msg = f"The account {username} is curently marked as inactive."
+                raise FetchError(msg)
         return accounts
 
     def _send_request(self, fetch_type, params, account):
@@ -141,7 +140,7 @@ def _send_request(self, fetch_type, params, account):
             response.raise_for_status()
         except requests.exceptions.HTTPError:
             # 4xx or 5xx errors:
-            error_message = "HTTP Error: %s" % response.status_code
+            error_message = f"HTTP Error: {response.status_code}"
         except NameError:
             if error_message == "":
                 error_message = "Something unusual went wrong."
@@ -251,7 +250,8 @@ def fetch(self, post_date, username=None):
         try:
             dt = datetime.strptime(post_date, "%Y-%m-%d").astimezone(timezone.utc)
         except ValueError as err:
-            raise FetchError("Invalid date format ('%s')" % post_date) from err
+            msg = f"Invalid date format ('{post_date}')"
+            raise FetchError(msg) from err
         else:
             return self._fetch(fetch_type="date", params={"dt": dt}, username=username)
 
diff --git a/ditto/twitter/admin.py b/ditto/twitter/admin.py
index 2ea2ef8..1846274 100644
--- a/ditto/twitter/admin.py
+++ b/ditto/twitter/admin.py
@@ -347,8 +347,6 @@ class UserAdmin(admin.ModelAdmin):
     )
 
     def show_avatar(self, instance):
-        return mark_safe(
-            '<img src="%s" width="24" height="24" />' % (instance.avatar_url)
-        )
+        return mark_safe(f'<img src="{instance.avatar_url}" width="24" height="24" />')
 
     show_avatar.short_description = ""
diff --git a/ditto/twitter/fetch/fetch.py b/ditto/twitter/fetch/fetch.py
index 3536162..5cdcfb6 100644
--- a/ditto/twitter/fetch/fetch.py
+++ b/ditto/twitter/fetch/fetch.py
@@ -77,7 +77,7 @@ def fetch(self):
         if self.account.user:
             self.return_value["account"] = self.account.user.screen_name
         elif self.account.pk:
-            self.return_value["account"] = "Account: %s" % str(self.account)
+            self.return_value["account"] = f"Account: {self.account}"
         else:
             self.return_value["account"] = "Unsaved Account"
 
@@ -110,7 +110,7 @@ def _fetch_pages(self):
             self._call_api()
         except TwythonError as e:
             self.return_value["success"] = False
-            self.return_value["messages"] = ["Error when calling API: %s" % e]
+            self.return_value["messages"] = [f"Error when calling API: {e}"]
         else:
             # If we've got to the last 'page' of tweet results, we'll receive
             # an empty list from the API.
diff --git a/ditto/twitter/fetch/fetchers.py b/ditto/twitter/fetch/fetchers.py
index 35cc184..88d54c7 100644
--- a/ditto/twitter/fetch/fetchers.py
+++ b/ditto/twitter/fetch/fetchers.py
@@ -109,15 +109,15 @@ def _set_accounts(self, screen_name=None):
             try:
                 accounts = [Account.objects.get(user__screen_name=screen_name)]
             except Account.DoesNotExist as err:
-                raise FetchError(
-                    "There is no Account in the database with a screen_name of '%s'"
-                    % screen_name
-                ) from err
+                msg = (
+                    "There is no Account in the database with a "
+                    f"screen_name of '{screen_name}'"
+                )
+                raise FetchError(msg) from err
             else:
                 if accounts[0].is_active is False:
-                    raise FetchError(
-                        "The '%s' Account is marked as inactive." % screen_name
-                    )
+                    msg = f"The '{screen_name}' Account is marked as inactive."
+                    raise FetchError(msg)
 
         self.accounts = accounts
 
diff --git a/ditto/twitter/ingest.py b/ditto/twitter/ingest.py
index 7af102c..c80c217 100644
--- a/ditto/twitter/ingest.py
+++ b/ditto/twitter/ingest.py
@@ -142,7 +142,8 @@ def _load_data(self, directory):
             raise IngestError(err) from err
 
         if self.file_count == 0:
-            raise IngestError("No .js files found in %s" % directory)
+            msg = f"No .js files found in {directory}"
+            raise IngestError(msg)
 
     def _get_data_from_file(self, filepath):
         """Looks in a file, parses its JSON, and adds a dict of data about
diff --git a/ditto/twitter/management/commands/__init__.py b/ditto/twitter/management/commands/__init__.py
index 8c65de8..923bcfa 100644
--- a/ditto/twitter/management/commands/__init__.py
+++ b/ditto/twitter/management/commands/__init__.py
@@ -73,9 +73,8 @@ def handle(self, *args, **options):
             try:
                 Account.objects.get(user__screen_name=screen_name)
             except Account.DoesNotExist as err:
-                raise CommandError(
-                    "There's no Account with a screen name of '%s'" % screen_name
-                ) from err
+                msg = "There's no Account with a screen name of '{screen_name}'"
+                raise CommandError(msg) from err
         else:
             msg = "Specify --account, eg --account=philgyford."
             raise CommandError(msg)
diff --git a/ditto/twitter/management/commands/fetch_twitter_accounts.py b/ditto/twitter/management/commands/fetch_twitter_accounts.py
index a55d6eb..f182bf7 100644
--- a/ditto/twitter/management/commands/fetch_twitter_accounts.py
+++ b/ditto/twitter/management/commands/fetch_twitter_accounts.py
@@ -41,7 +41,7 @@ def handle(self, *args, **options):
         if options.get("verbosity", 1) > 0:
             for result in results:
                 if result["success"]:
-                    self.stdout.write("Fetched @%s" % result["account"])
+                    self.stdout.write(f"Fetched @{result['account']}")
                 else:
                     self.stderr.write(
                         "Could not fetch @{}: {}".format(
diff --git a/ditto/twitter/management/commands/generate_twitter_tweet_html.py b/ditto/twitter/management/commands/generate_twitter_tweet_html.py
index d62cb6e..b598d2c 100644
--- a/ditto/twitter/management/commands/generate_twitter_tweet_html.py
+++ b/ditto/twitter/management/commands/generate_twitter_tweet_html.py
@@ -33,9 +33,8 @@ def handle(self, *args, **options):
             try:
                 Account.objects.get(user__screen_name=screen_name)
             except Account.DoesNotExist as err:
-                raise CommandError(
-                    "There's no Account with a screen name of '%s'" % screen_name
-                ) from err
+                msg = f"There's no Account with a screen name of '{screen_name}'"
+                raise CommandError(msg) from err
             tweets = tweets.filter(user__screen_name=screen_name)
 
         for tweet in tweets:
diff --git a/ditto/twitter/models.py b/ditto/twitter/models.py
index f173c71..e757fd3 100644
--- a/ditto/twitter/models.py
+++ b/ditto/twitter/models.py
@@ -807,7 +807,7 @@ class Meta:
         ordering = ["screen_name"]
 
     def __str__(self):
-        return "@%s" % self.screen_name
+        return f"@{self.screen_name}"
 
     def save(self, *args, **kwargs):
         """If the user's privacy status has changed, we need to change the
@@ -835,7 +835,7 @@ def make_description_html(self):
 
     @property
     def permalink(self):
-        return "https://twitter.com/%s" % self.screen_name
+        return f"https://twitter.com/{self.screen_name}"
 
     @property
     def avatar_url(self):
diff --git a/ditto/twitter/utils.py b/ditto/twitter/utils.py
index 32533ac..8b97f1c 100644
--- a/ditto/twitter/utils.py
+++ b/ditto/twitter/utils.py
@@ -118,8 +118,8 @@ def htmlify_tweet(json_data):
     if (urls_count + media_count) > 0 and urls_count > 0:
         for url in ents["urls"]:
             html = html.replace(
-                '<a href="%s" class="twython-url">' % url["url"],
-                '<a href="%s" rel="external">' % url["expanded_url"],
+                f'<a href="{url['url']}" class="twython-url">',
+                f'<a href="{url['expanded_url']}" rel="external">',
             )
 
     if media_count > 0:
diff --git a/docs/conf.py b/docs/conf.py
index 176e121..9794b68 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -69,7 +69,7 @@ def get_entity(package, entity):
     path = os.path.join(os.path.dirname(__file__), "..", "ditto", "__init__.py")
     with open(path) as f:
         init_py = f.read()
-        find = "__%s__ = ['\"]([^'\"]+)['\"]" % entity
+        find = f"__{entity}__ = ['\"]([^'\"]+)['\"]"
         return re.search(find, init_py).group(1)
 
 
diff --git a/setup.py b/setup.py
index 3d23ad1..0685fdb 100644
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,7 @@ def get_entity(package, entity):
     """
     with open(os.path.join(package, "__init__.py")) as f:
         init_py = f.read()
-        find = "__%s__ = ['\"]([^'\"]+)['\"]" % entity
+        find = f"__{entity}__ = ['\"]([^'\"]+)['\"]"
         return re.search(find, init_py).group(1)
 
 
@@ -53,8 +53,7 @@ def get_author_email():
 if sys.argv[-1] == "publish":
     os.system("python setup.py sdist")
     os.system(
-        "twine upload --config-file=.pypirc dist/django-ditto-%s.tar.gz"
-        % (get_version())
+        f"twine upload --config-file=.pypirc dist/django-ditto-{get_version()}.tar.gz"
     )
     sys.exit()
 
@@ -63,8 +62,7 @@ def get_author_email():
 if sys.argv[-1] == "testpublish":
     os.system("python setup.py sdist")
     os.system(
-        "twine upload --config-file=.pypirc --repository-url https://test.pypi.org/legacy/ dist/django-ditto-%s.tar.gz"  # noqa: E501
-        % (get_version())
+        f"twine upload --config-file=.pypirc --repository-url https://test.pypi.org/legacy/ dist/django-ditto-{get_version()}.tar.gz"  # noqa: E501
     )
     # os.system("python setup.py bdist_wheel upload")
     sys.exit()
diff --git a/tests/flickr/test_fetch_fetchers.py b/tests/flickr/test_fetch_fetchers.py
index b00d9d7..e2ba188 100644
--- a/tests/flickr/test_fetch_fetchers.py
+++ b/tests/flickr/test_fetch_fetchers.py
@@ -184,10 +184,8 @@ def test_downloads_and_saves_avatar(self, download):
             ["image/jpeg", "image/jpg", "image/png", "image/gif"],
         )
 
-        self.assertEqual(
-            user.avatar,
-            "flickr/60/50/35034346050N01/avatars/%s" % os.path.basename(temp_filepath),
-        )
+        path = os.path.basename(temp_filepath)
+        self.assertEqual(user.avatar, f"flickr/60/50/35034346050N01/avatars/{path}")
 
     def test_returns_correct_success_result(self):
         self.expect_response("people.getInfo")
diff --git a/tests/flickr/test_models.py b/tests/flickr/test_models.py
index 0921ba2..b7a0c7f 100644
--- a/tests/flickr/test_models.py
+++ b/tests/flickr/test_models.py
@@ -440,7 +440,7 @@ def test_image_urls(self):
         for size, prop in self.photo_sizes.items():
             self.assertEqual(
                 getattr(photo, prop),
-                "https://farm3.static.flickr.com/1234/4567_9876_%s.jpg" % size,
+                f"https://farm3.static.flickr.com/1234/4567_9876_{size}.jpg",
             )
 
     def test_image_url_with_invalid_size(self):
@@ -489,7 +489,7 @@ def test_original_url(self):
         filename = os.path.basename(self.photo.original_file.name)
         self.assertEqual(
             self.photo.original_url,
-            "/media/flickr/34/56/123456N01/photos/2015/08/14/%s" % filename,
+            f"/media/flickr/34/56/123456N01/photos/2015/08/14/{filename}",
         )
 
     def test_remote_original_url(self):
diff --git a/tests/lastfm/test_fetch.py b/tests/lastfm/test_fetch.py
index bb17b50..bffefc6 100644
--- a/tests/lastfm/test_fetch.py
+++ b/tests/lastfm/test_fetch.py
@@ -171,11 +171,11 @@ def add_recent_tracks_response(self, body=None, page=1, status=200, from_time=No
 
         url = (
             "http://ws.audioscrobbler.com/2.0/?method=user.getrecenttracks&user=bob&"
-            "api_key=1234&format=json&page=%s&limit=200" % page
+            f"api_key=1234&format=json&page={page}&limit=200"
         )
 
         if from_time is not None:
-            url += "&from=%s" % from_time
+            url += f"&from={from_time}"
 
         if body is None:
             # Default success response
diff --git a/tests/lastfm/test_views.py b/tests/lastfm/test_views.py
index 2995c02..f496121 100644
--- a/tests/lastfm/test_views.py
+++ b/tests/lastfm/test_views.py
@@ -118,7 +118,8 @@ def test_all_days(self):
             album=album,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=all" % reverse("lastfm:album_list"))
+        url = reverse("lastfm:album_list")
+        response = self.client.get(f"{url}?days=all")
         self.assertEqual(response.context["album_list"][0].scrobble_count, 2)
 
     @freeze_time("2016-10-05 12:00:00", tz_offset=-8)
@@ -136,7 +137,8 @@ def test_7_days(self):
             album=album,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=7" % reverse("lastfm:album_list"))
+        url = reverse("lastfm:album_list")
+        response = self.client.get(f"{url}?days=7")
         self.assertEqual(response.context["album_list"][0].scrobble_count, 1)
 
 
@@ -258,7 +260,8 @@ def test_all_days(self):
             track=track,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=all" % reverse("lastfm:artist_list"))
+        url = reverse("lastfm:artist_list")
+        response = self.client.get(f"{url}?days=all")
         self.assertEqual(response.context["artist_list"][0].scrobble_count, 2)
 
     @freeze_time("2016-10-05 12:00:00", tz_offset=-8)
@@ -276,7 +279,8 @@ def test_7_days(self):
             track=track,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=7" % reverse("lastfm:artist_list"))
+        url = reverse("lastfm:artist_list")
+        response = self.client.get(f"{url}?days=7")
         self.assertEqual(response.context["artist_list"][0].scrobble_count, 1)
 
 
@@ -424,7 +428,8 @@ def test_all_days(self):
             track=track,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=all" % reverse("lastfm:track_list"))
+        url = reverse("lastfm:track_list")
+        response = self.client.get(f"{url}?days=all")
         self.assertEqual(response.context["track_list"][0].scrobble_count, 2)
 
     @freeze_time("2016-10-05 12:00:00", tz_offset=-8)
@@ -442,7 +447,8 @@ def test_7_days(self):
             track=track,
             post_time=datetime_from_str("2016-10-01 12:00:00"),
         )
-        response = self.client.get("%s?days=7" % reverse("lastfm:track_list"))
+        url = reverse("lastfm:track_list")
+        response = self.client.get(f"{url}?days=7")
         self.assertEqual(response.context["track_list"][0].scrobble_count, 1)
 
 
@@ -489,10 +495,10 @@ def setUp(self):
     def test_templates(self):
         "Uses the correct templates"
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertEqual(response.status_code, 200)
-        self.assertTemplateUsed(response, "lastfm/%s.html" % self.view_name)
+        self.assertTemplateUsed(response, f"lastfm/{self.view_name}.html")
         self.assertTemplateUsed(response, "lastfm/base.html")
         self.assertTemplateUsed(response, "ditto/base.html")
 
@@ -501,7 +507,7 @@ def test_context_counts(self):
         All user_* views should have these same counts in their context.
         """
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertIn("counts", response.context)
         self.assertEqual(response.context["counts"]["albums"], 1)
@@ -512,7 +518,7 @@ def test_context_counts(self):
     def test_404s(self):
         "Responds with 404 if we request a user that doesn't exist."
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "thelma"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "thelma"})
         )
         self.assertEqual(response.status_code, 404)
 
@@ -527,7 +533,7 @@ class UserAlbumListViewTestCase(UserCommonTests, TestCase):
     def test_context_albums(self):
         "Sends the correct album data to the templates"
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertIn("album_list", response.context)
         albums = response.context["album_list"]
@@ -542,7 +548,7 @@ class UserArtistListViewTestCase(UserCommonTests, TestCase):
     def test_context_albums(self):
         "Sends the correct album data to the templates"
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertIn("artist_list", response.context)
         artists = response.context["artist_list"]
@@ -559,7 +565,7 @@ class UserScrobbleListViewTestCase(UserCommonTests, TestCase):
     def test_context_scrobbles(self):
         "Sends the correct scrobble data to the templates"
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertIn("scrobble_list", response.context)
         scrobbles = response.context["scrobble_list"]
@@ -572,7 +578,7 @@ class UserTrackListViewTestCase(UserCommonTests, TestCase):
     def test_context_tracks(self):
         "Sends the correct track data to the templates"
         response = self.client.get(
-            reverse("lastfm:%s" % self.view_name, kwargs={"username": "bob"})
+            reverse(f"lastfm:{self.view_name}", kwargs={"username": "bob"})
         )
         self.assertIn("track_list", response.context)
         tracks = response.context["track_list"]
diff --git a/tests/pinboard/test_fetch.py b/tests/pinboard/test_fetch.py
index 8d2a491..b3730a2 100644
--- a/tests/pinboard/test_fetch.py
+++ b/tests/pinboard/test_fetch.py
@@ -50,7 +50,7 @@ def add_response(self, body, method="get", status=200):
         """
         responses.add(
             responses.GET,
-            "https://api.pinboard.in/v1/posts/%s" % method,
+            f"https://api.pinboard.in/v1/posts/{method}",
             status=status,
             match_querystring=False,
             body=body,
@@ -69,7 +69,8 @@ def make_success_body(
                 % (n, n, n, post_date)
             )
 
-        posts_json = "[%s]\t\n" % (",".join(posts))
+        posts_str = ",".join(posts)
+        posts_json = f"[{posts_str}]\t\n"
 
         if method == "all":
             return posts_json
diff --git a/tests/twitter/test_fetch_savers.py b/tests/twitter/test_fetch_savers.py
index 97a7acb..e0e3e79 100644
--- a/tests/twitter/test_fetch_savers.py
+++ b/tests/twitter/test_fetch_savers.py
@@ -492,10 +492,8 @@ def test_downloads_and_saves_avatar(self, download):
             ["image/jpeg", "image/jpg", "image/png", "image/gif"],
         )
 
-        self.assertEqual(
-            saved_user.avatar,
-            "twitter/avatars/25/52/12552/%s" % os.path.basename(temp_filepath),
-        )
+        path = os.path.basename(temp_filepath)
+        self.assertEqual(saved_user.avatar, f"twitter/avatars/25/52/12552/{path}")
 
     @patch.object(filedownloader, "download")
     @patch.object(os.path, "exists")
diff --git a/tests/twitter/test_models.py b/tests/twitter/test_models.py
index ff6ee0b..149adea 100644
--- a/tests/twitter/test_models.py
+++ b/tests/twitter/test_models.py
@@ -60,7 +60,7 @@ def test_str_2(self):
         "Has the correct string represntation when it has a user"
         user = UserFactory()
         account = AccountFactory(user=user)
-        self.assertEqual(account.__str__(), "@%s" % user.screen_name)
+        self.assertEqual(account.__str__(), f"@{user.screen_name}")
 
     def test_ordering(self):
         """Multiple accounts are by user.screen_name time ascending"""
@@ -217,11 +217,11 @@ def test_default_manager(self):
     def test_size_urls(self):
         url = "http://www.example.org/image.jpg"
         photo = PhotoFactory(image_url=url)
-        self.assertEqual(photo.large_url, "%s:large" % url)
-        self.assertEqual(photo.medium_url, "%s:medium" % url)
-        self.assertEqual(photo.small_url, "%s:small" % url)
-        self.assertEqual(photo.thumb_url, "%s:thumb" % url)
-        self.assertEqual(photo.thumbnail_url, "%s:thumb" % url)
+        self.assertEqual(photo.large_url, f"{url}:large")
+        self.assertEqual(photo.medium_url, f"{url}:medium")
+        self.assertEqual(photo.small_url, f"{url}:small")
+        self.assertEqual(photo.thumb_url, f"{url}:thumb")
+        self.assertEqual(photo.thumbnail_url, f"{url}:thumb")
 
     def test_tweets(self):
         "It should be possible to belong to more than one tweet."
@@ -392,7 +392,7 @@ def tearDown(self):
     def test_video_url_mp4(self):
         gif = AnimatedGifFactory(mp4_url="https://example.org/test.mp4")
         filename = os.path.basename(gif.mp4_file.name)
-        self.assertEqual(gif.video_url, "/media/twitter/media/mp/le/%s" % filename)
+        self.assertEqual(gif.video_url, f"/media/twitter/media/mp/le/{filename}")
 
 
 class TweetTestCase(TestCase):