minor syntax or performance improvements

whitenoise/base.py

@@ -108,17 +108,16 @@ def add_files(self, root, prefix=None):
             # to store the list of directories in reverse order so later ones
             # match first when they're checked in "autorefresh" mode
             self.directories.insert(0, (root, prefix))
+        elif os.path.isdir(root):
+            self.update_files_dictionary(root, prefix)
         else:
-            if os.path.isdir(root):
-                self.update_files_dictionary(root, prefix)
-            else:
-                warnings.warn(f"No directory at: {root}")
+            warnings.warn(f"No directory at: {root}")
 
     def update_files_dictionary(self, root, prefix):
         # Build a mapping from paths to the results of `os.stat` calls
         # so we only have to touch the filesystem once
         stat_cache = dict(scantree(root))
-        for path in stat_cache.keys():
+        for path in stat_cache:
             relative_path = path[len(root) :]
             relative_url = relative_path.replace("\\", "/")
             url = prefix + relative_url

whitenoise/middleware.py

@@ -85,9 +85,8 @@ def configure_from_settings(self, settings):
         self.use_finders = settings.DEBUG
         self.static_prefix = urlparse(settings.STATIC_URL or "").path
         script_prefix = get_script_prefix().rstrip("/")
-        if script_prefix:
-            if self.static_prefix.startswith(script_prefix):
-                self.static_prefix = self.static_prefix[len(script_prefix) :]
+        if script_prefix and self.static_prefix.startswith(script_prefix):
+            self.static_prefix = self.static_prefix[len(script_prefix) :]
         if settings.DEBUG:
             self.max_age = 0
         # Allow settings to override default attributes
@@ -128,8 +127,7 @@ def candidate_paths_for_url(self, url):
             if path:
                 yield path
         paths = super().candidate_paths_for_url(url)
-        for path in paths:
-            yield path
+        yield from paths
 
     def immutable_file_test(self, path, url):
         """