diff --git a/social_core/backends/base.py b/social_core/backends/base.py
index 71a1c8bce..be8f5ec1c 100644
--- a/social_core/backends/base.py
+++ b/social_core/backends/base.py
@@ -190,7 +190,7 @@ def get_user_names(self, fullname="", first_name="", last_name=""):
             except ValueError:
                 first_name = first_name or fullname or ""
                 last_name = last_name or ""
-        fullname = fullname or " ".join((first_name, last_name))
+        fullname = fullname or f"{first_name} {last_name}"
         return fullname.strip(), first_name.strip(), last_name.strip()
 
     def get_user(self, user_id):
diff --git a/social_core/backends/lastfm.py b/social_core/backends/lastfm.py
index 735d3d422..941c634fb 100644
--- a/social_core/backends/lastfm.py
+++ b/social_core/backends/lastfm.py
@@ -28,9 +28,7 @@ def auth_complete(self, *args, **kwargs):
         token = self.data["token"]
 
         signature = hashlib.md5(
-            "".join(
-                ("api_key", key, "methodauth.getSession", "token", token, secret)
-            ).encode()
+            f"api_key{key}methodauth.getSessiontoken{token}{secret}".encode()
         ).hexdigest()
 
         response = self.get_json(
diff --git a/social_core/backends/yahoo.py b/social_core/backends/yahoo.py
index a5ef64b7c..20c18da98 100644
--- a/social_core/backends/yahoo.py
+++ b/social_core/backends/yahoo.py
@@ -74,7 +74,7 @@ class YahooOAuth2(BaseOAuth2):
 
     def get_user_names(self, first_name, last_name):
         if first_name or last_name:
-            return " ".join((first_name, last_name)), first_name, last_name
+            return f"{first_name} {last_name}", first_name, last_name
         return None, None, None
 
     def get_user_details(self, response):
diff --git a/social_core/tests/backends/test_livejournal.py b/social_core/tests/backends/test_livejournal.py
index b25836613..aaba8790a 100644
--- a/social_core/tests/backends/test_livejournal.py
+++ b/social_core/tests/backends/test_livejournal.py
@@ -14,19 +14,15 @@
 class LiveJournalOpenIdTest(OpenIdTest):
     backend_path = "social_core.backends.livejournal.LiveJournalOpenId"
     expected_username = "foobar"
-    discovery_body = "".join(
-        [
-            '<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">',
-            "<XRD>",
-            '<Service priority="0">',
-            "<Type>http://specs.openid.net/auth/2.0/signon</Type>",
-            "<URI>http://www.livejournal.com/openid/server.bml</URI>",
-            "<LocalID>http://foobar.livejournal.com/</LocalID>",
-            "</Service>",
-            "</XRD>",
-            "</xrds:XRDS>",
-        ]
-    )
+    discovery_body = """<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
+    <XRD>
+        <Service priority="0">
+            <Type>http://specs.openid.net/auth/2.0/signon</Type>
+            <URI>http://www.livejournal.com/openid/server.bml</URI>
+            <LocalID>http://foobar.livejournal.com/</LocalID>
+        </Service>
+    </XRD>
+</xrds:XRDS>"""
     server_response = urlencode(
         {
             "janrain_nonce": JANRAIN_NONCE,
@@ -44,20 +40,14 @@ class LiveJournalOpenIdTest(OpenIdTest):
             "openid.sig": "Z8MOozVPTOBhHG5ZS1NeGofxs1Q=",
         }
     )
-    server_bml_body = "\n".join(
-        [
-            "assoc_handle:1364935340:ZhruPQ7DJ9eGgUkeUA9A:27f8c32464",
-            "assoc_type:HMAC-SHA1",
-            "dh_server_public:WzsRyLomvAV3vwvGUrfzXDgfqnTF+m1l3JWb55fyHO7visPT4tmQ"
-            "iTjqFFnSVAtAOvQzoViMiZQisxNwnqSK4lYexoez1z6pP5ry3pqxJAEYj60vFGvRztict"
-            "Eo0brjhmO1SNfjK1ppjOymdykqLpZeaL5fsuLtMCwTnR/JQZVA=",
-            "enc_mac_key:LiOEVlLJSVUqfNvb5zPd76nEfvc=",
-            "expires_in:1207060",
-            "ns:http://specs.openid.net/auth/2.0",
-            "session_type:DH-SHA1",
-            "",
-        ]
-    )
+    server_bml_body = """assoc_handle:1364935340:ZhruPQ7DJ9eGgUkeUA9A:27f8c32464
+assoc_type:HMAC-SHA1
+dh_server_public:WzsRyLomvAV3vwvGUrfzXDgfqnTF+m1l3JWb55fyHO7visPT4tmQiTjqFFnSVAtAOvQzoViMiZQisxNwnqSK4lYexoez1z6pP5ry3pqxJAEYj60vFGvRztictEo0brjhmO1SNfjK1ppjOymdykqLpZeaL5fsuLtMCwTnR/JQZVA=
+enc_mac_key:LiOEVlLJSVUqfNvb5zPd76nEfvc=
+expires_in:1207060
+ns:http://specs.openid.net/auth/2.0
+session_type:DH-SHA1
+"""
 
     def openid_url(self):
         return super().openid_url() + "/data/yadis"
diff --git a/social_core/tests/backends/test_ngpvan.py b/social_core/tests/backends/test_ngpvan.py
index 9173ff6e6..66ca3b513 100644
--- a/social_core/tests/backends/test_ngpvan.py
+++ b/social_core/tests/backends/test_ngpvan.py
@@ -17,30 +17,23 @@ class NGPVANActionIDOpenIDTest(OpenIdTest):
 
     backend_path = "social_core.backends.ngpvan.ActionIDOpenID"
     expected_username = "testuser@user.local"
-    discovery_body = " ".join(
-        [
-            '<?xml version="1.0" encoding="UTF-8"?>',
-            "<xrds:XRDS",
-            'xmlns:xrds="xri://$xrds"',
-            'xmlns:openid="http://openid.net/xmlns/1.0"',
-            'xmlns="xri://$xrd*($v*2.0)">',
-            "<XRD>",
-            '<Service priority="10">',
-            "<Type>http://specs.openid.net/auth/2.0/signon</Type>",
-            "<Type>http://openid.net/extensions/sreg/1.1</Type>",
-            "<Type>http://axschema.org/contact/email</Type>",
-            "<URI>https://accounts.ngpvan.com/OpenId/Provider</URI>",
-            "</Service>",
-            '<Service priority="20">',
-            "<Type>http://openid.net/signon/1.0</Type>",
-            "<Type>http://openid.net/extensions/sreg/1.1</Type>",
-            "<Type>http://axschema.org/contact/email</Type>",
-            "<URI>https://accounts.ngpvan.com/OpenId/Provider</URI>",
-            "</Service>",
-            "</XRD>",
-            "</xrds:XRDS>",
-        ]
-    )
+    discovery_body = """<?xml version="1.0" encoding="UTF-8"?>
+<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns:openid="http://openid.net/xmlns/1.0" xmlns="xri://$xrd*($v*2.0)">
+    <XRD>
+        <Service priority="10">
+            <Type>http://specs.openid.net/auth/2.0/signon</Type>
+            <Type>http://openid.net/extensions/sreg/1.1</Type>
+            <Type>http://axschema.org/contact/email</Type>
+            <URI>https://accounts.ngpvan.com/OpenId/Provider</URI>
+        </Service>
+        <Service priority="20">
+            <Type>http://openid.net/signon/1.0</Type>
+            <Type>http://openid.net/extensions/sreg/1.1</Type>
+            <Type>http://axschema.org/contact/email</Type>
+            <URI>https://accounts.ngpvan.com/OpenId/Provider</URI>
+        </Service>
+    </XRD>
+</xrds:XRDS>"""
     server_response = urlencode(
         {
             "openid.claimed_id": "https://accounts.ngpvan.com/user/abcd123",
diff --git a/social_core/tests/backends/test_open_id_connect.py b/social_core/tests/backends/test_open_id_connect.py
index f57db5967..19c5d963e 100644
--- a/social_core/tests/backends/test_open_id_connect.py
+++ b/social_core/tests/backends/test_open_id_connect.py
@@ -166,7 +166,7 @@ def prepare_access_token_body(
             header, msg, sig = body["id_token"].split(".")
             id_token["sub"] = "1235"
             msg = base64.encodebytes(json.dumps(id_token).encode()).decode()
-            body["id_token"] = ".".join([header, msg, sig])
+            body["id_token"] = f"{header}.{msg}.{sig}"
 
         return json.dumps(body)
 
diff --git a/social_core/tests/backends/test_steam.py b/social_core/tests/backends/test_steam.py
index 6798e453c..9f11afad5 100644
--- a/social_core/tests/backends/test_steam.py
+++ b/social_core/tests/backends/test_steam.py
@@ -14,32 +14,24 @@
 class SteamOpenIdTest(OpenIdTest):
     backend_path = "social_core.backends.steam.SteamOpenId"
     expected_username = "foobar"
-    discovery_body = "".join(
-        [
-            '<?xml version="1.0" encoding="UTF-8"?>',
-            '<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">',
-            "<XRD>",
-            '<Service priority="0">',
-            "<Type>http://specs.openid.net/auth/2.0/server</Type>",
-            "<URI>https://steamcommunity.com/openid/login</URI>",
-            "</Service>",
-            "</XRD>",
-            "</xrds:XRDS>",
-        ]
-    )
-    user_discovery_body = "".join(
-        [
-            '<?xml version="1.0" encoding="UTF-8"?>',
-            '<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">',
-            "<XRD>",
-            '<Service priority="0">',
-            "<Type>http://specs.openid.net/auth/2.0/signon</Type>		",
-            "<URI>https://steamcommunity.com/openid/login</URI>",
-            "</Service>",
-            "</XRD>",
-            "</xrds:XRDS>",
-        ]
-    )
+    discovery_body = """<?xml version="1.0" encoding="UTF-8"?>
+<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
+    <XRD>
+        <Service priority="0">
+            <Type>http://specs.openid.net/auth/2.0/server</Type>
+            <URI>https://steamcommunity.com/openid/login</URI>
+        </Service>
+    </XRD>
+</xrds:XRDS>"""
+    user_discovery_body = """<?xml version="1.0" encoding="UTF-8"?>
+<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
+    <XRD>
+        <Service priority="0">
+            <Type>http://specs.openid.net/auth/2.0/signon</Type>
+            <URI>https://steamcommunity.com/openid/login</URI>
+        </Service>
+    </XRD>
+</xrds:XRDS>"""
     server_response = urlencode(
         {
             "janrain_nonce": JANRAIN_NONCE,