diff --git a/m3u8/model.py b/m3u8/model.py
index 9bc16071..1dc7a5e4 100644
--- a/m3u8/model.py
+++ b/m3u8/model.py
@@ -657,9 +657,9 @@ def dumps(self, last_segment, timespec="milliseconds", infspec="auto"):
         if self.uri:
             if self.duration is not None:
                 if infspec == "milliseconds":
-                    duration = "{:.3f}".format(self.duration)
+                    duration = f"{self.duration:.3f}"
                 elif infspec == "microseconds":
-                    duration = "{:.6f}".format(self.duration)
+                    duration = f"{self.duration:.6f}"
                 else:
                     duration = number_to_string(self.duration)
                 output.append("#EXTINF:%s," % duration)
diff --git a/tests/test_model.py b/tests/test_model.py
index 8185fe38..da47a483 100755
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -764,7 +764,7 @@ def test_create_sub_directories_with_relative_path(tmpdir, monkeypatch):
     expected_file_path = os.path.join(tmpdir, relative_path)
     assert os.path.exists(expected_file_path)
 
-    with open(expected_file_path, "r") as file:
+    with open(expected_file_path) as file:
         assert file.read().strip() == playlists.SIMPLE_PLAYLIST.strip()