Replaced temporary lists used for passing arguments with iterables.

django/core/checks/registry.py

@@ -86,7 +86,10 @@ class CheckRegistry:
         return tag in self.tags_available(include_deployment_checks)
 
     def tags_available(self, deployment_checks=False):
-        return set(chain(*[check.tags for check in self.get_checks(deployment_checks) if hasattr(check, 'tags')]))
+        return set(chain.from_iterable(
+            check.tags for check in self.get_checks(deployment_checks)
+            if hasattr(check, 'tags')
+        ))
 
     def get_checks(self, include_deployment_checks=False):
         checks = list(self.registered_checks)

django/core/management/commands/makemigrations.py

@@ -244,7 +244,7 @@ class Command(BaseCommand):
             def all_items_equal(seq):
                 return all(item == seq[0] for item in seq[1:])
 
-            merge_migrations_generations = zip(*[m.ancestry for m in merge_migrations])
+            merge_migrations_generations = zip(*(m.ancestry for m in merge_migrations))
             common_ancestor_count = sum(1 for common_ancestor_generation
                                         in takewhile(all_items_equal, merge_migrations_generations))
             if not common_ancestor_count:

django/forms/widgets.py

@@ -51,7 +51,7 @@ class Media:
         return self.render()
 
     def render(self):
-        return mark_safe('\n'.join(chain(*[getattr(self, 'render_' + name)() for name in MEDIA_TYPES])))
+        return mark_safe('\n'.join(chain.from_iterable(getattr(self, 'render_' + name)() for name in MEDIA_TYPES)))
 
     def render_js(self):
         return [
@@ -65,12 +65,12 @@ class Media:
         # To keep rendering order consistent, we can't just iterate over items().
         # We need to sort the keys, and iterate over the sorted list.
         media = sorted(self._css.keys())
-        return chain(*[[
+        return chain.from_iterable([
             format_html(
                 '<link href="{}" type="text/css" media="{}" rel="stylesheet" />',
                 self.absolute_path(path), medium
             ) for path in self._css[medium]
-        ] for medium in media])
+        ] for medium in media)
 
     def absolute_path(self, path):
         """

django/template/context_processors.py

@@ -43,7 +43,7 @@ def debug(request):
         # Return a lazy reference that computes connection.queries on access,
         # to ensure it contains queries triggered after this function runs.
         context_extras['sql_queries'] = lazy(
-            lambda: list(itertools.chain(*[connections[x].queries for x in connections])),
+            lambda: list(itertools.chain.from_iterable(connections[x].queries for x in connections)),
             list
         )
     return context_extras