Refs #28909 -- Simplifed code using unpacking generalizations.

django/db/backends/base/base.py

@@ -589,13 +589,11 @@ class BaseDatabaseWrapper:
         potential child threads while (or after) the test database is destroyed.
         Refs #10868, #17786, #16969.
         """
-        settings_dict = self.settings_dict.copy()
+        return self.__class__(
-        settings_dict['NAME'] = None
+            {**self.settings_dict, 'NAME': None},
-        nodb_connection = self.__class__(
-            settings_dict,
             alias=NO_DB_ALIAS,
-            allow_thread_sharing=False)
+            allow_thread_sharing=False,
-        return nodb_connection
+        )
 
     def _start_transaction_under_autocommit(self):
         """

django/db/backends/base/creation.py

@@ -221,9 +221,7 @@ class BaseDatabaseCreation:
         # already and its name has been copied to settings_dict['NAME'] so
         # we don't need to call _get_test_db_name.
         orig_settings_dict = self.connection.settings_dict
-        new_settings_dict = orig_settings_dict.copy()
+        return {**orig_settings_dict, 'NAME': '{}_{}'.format(orig_settings_dict['NAME'], suffix)}
-        new_settings_dict['NAME'] = '{}_{}'.format(orig_settings_dict['NAME'], suffix)
-        return new_settings_dict
 
     def _clone_test_db(self, suffix, verbosity, keepdb=False):
         """

django/db/backends/sqlite3/creation.py

@@ -51,10 +51,8 @@ class DatabaseCreation(BaseDatabaseCreation):
         if self.is_in_memory_db(source_database_name):
             return orig_settings_dict
         else:
-            new_settings_dict = orig_settings_dict.copy()
             root, ext = os.path.splitext(orig_settings_dict['NAME'])
-            new_settings_dict['NAME'] = '{}_{}.{}'.format(root, suffix, ext)
+            return {**orig_settings_dict, 'NAME': '{}_{}.{}'.format(root, suffix, ext)}
-            return new_settings_dict
 
     def _clone_test_db(self, suffix, verbosity, keepdb=False):
         source_database_name = self.connection.settings_dict['NAME']

django/db/models/query.py

@@ -219,9 +219,7 @@ class QuerySet:
     def __getstate__(self):
         # Force the cache to be fully populated.
         self._fetch_all()
-        obj_dict = self.__dict__.copy()
+        return {**self.__dict__, DJANGO_VERSION_PICKLE_KEY: get_version()}
-        obj_dict[DJANGO_VERSION_PICKLE_KEY] = get_version()
-        return obj_dict
 
     def __setstate__(self, state):
         msg = None

django/forms/widgets.py

@@ -958,35 +958,29 @@ class SelectDateWidget(Widget):
         year_choices = [(i, str(i)) for i in self.years]
         if not self.is_required:
             year_choices.insert(0, self.year_none_value)
-        year_attrs = context['widget']['attrs'].copy()
         year_name = self.year_field % name
-        year_attrs['id'] = 'id_%s' % year_name
         date_context['year'] = self.select_widget(attrs, choices=year_choices).get_context(
             name=year_name,
             value=context['widget']['value']['year'],
-            attrs=year_attrs,
+            attrs={**context['widget']['attrs'], 'id': 'id_%s' % year_name},
         )
         month_choices = list(self.months.items())
         if not self.is_required:
             month_choices.insert(0, self.month_none_value)
-        month_attrs = context['widget']['attrs'].copy()
         month_name = self.month_field % name
-        month_attrs['id'] = 'id_%s' % month_name
         date_context['month'] = self.select_widget(attrs, choices=month_choices).get_context(
             name=month_name,
             value=context['widget']['value']['month'],
-            attrs=month_attrs,
+            attrs={**context['widget']['attrs'], 'id': 'id_%s' % month_name},
         )
         day_choices = [(i, i) for i in range(1, 32)]
         if not self.is_required:
             day_choices.insert(0, self.day_none_value)
-        day_attrs = context['widget']['attrs'].copy()
         day_name = self.day_field % name
-        day_attrs['id'] = 'id_%s' % day_name
         date_context['day'] = self.select_widget(attrs, choices=day_choices,).get_context(
             name=day_name,
             value=context['widget']['value']['day'],
-            attrs=day_attrs,
+            attrs={**context['widget']['attrs'], 'id': 'id_%s' % day_name},
         )
         subwidgets = []
         for field in self._parse_date_fmt():

django/template/utils.py

@@ -30,7 +30,6 @@ class EngineHandler:
         templates = OrderedDict()
         backend_names = []
         for tpl in self._templates:
-            tpl = tpl.copy()
             try:
                 # This will raise an exception if 'BACKEND' doesn't exist or
                 # isn't a string containing at least one dot.
@@ -41,10 +40,13 @@ class EngineHandler:
                     "Invalid BACKEND for a template engine: {}. Check "
                     "your TEMPLATES setting.".format(invalid_backend))
 
-            tpl.setdefault('NAME', default_name)
+            tpl = {
-            tpl.setdefault('DIRS', [])
+                'NAME': default_name,
-            tpl.setdefault('APP_DIRS', False)
+                'DIRS': [],
-            tpl.setdefault('OPTIONS', {})
+                'APP_DIRS': False,
+                'OPTIONS': {},
+                **tpl,
+            }
 
             templates[tpl['NAME']] = tpl
             backend_names.append(tpl['NAME'])

django/utils/autoreload.py

@@ -289,8 +289,7 @@ def restart_with_reloader():
             args += sys.argv[1:]
         else:
             args += sys.argv
-        new_environ = os.environ.copy()
+        new_environ = {**os.environ, 'RUN_MAIN': 'true'}
-        new_environ["RUN_MAIN"] = 'true'
         exit_code = subprocess.call(args, env=new_environ)
         if exit_code != 3:
             return exit_code

django/utils/datastructures.py

@@ -100,9 +100,7 @@ class MultiValueDict(dict):
         return result
 
     def __getstate__(self):
-        obj_dict = self.__dict__.copy()
+        return {**self.__dict__, '_data': {k: self._getlist(k) for k in self}}
-        obj_dict['_data'] = {k: self._getlist(k) for k in self}
-        return obj_dict
 
     def __setstate__(self, obj_dict):
         data = obj_dict.pop('_data', {})