Fixed #28984 -- Made assorted code simplifications.

django/contrib/admin/helpers.py

@@ -203,8 +203,7 @@ def contents(self):
             result_repr = self.empty_value_display
         else:
             if f is None:
-                boolean = getattr(attr, "boolean", False)
-                if boolean:
+                if getattr(attr, 'boolean', False):
                     result_repr = _boolean_icon(value)
                 else:
                     if hasattr(value, "__html__"):
@@ -331,14 +330,14 @@ def __iter__(self):
             )
 
     def needs_explicit_pk_field(self):
-        # Auto fields are editable (oddly), so need to check for auto or non-editable pk
-        if self.form._meta.model._meta.auto_field or not self.form._meta.model._meta.pk.editable:
-            return True
-        # Also search any parents for an auto field. (The pk info is propagated to child
-        # models so that does not need to be checked in parents.)
-        return any(
-            parent._meta.auto_field or not parent._meta.model._meta.pk.editable
-            for parent in self.form._meta.model._meta.get_parent_list()
+        return (
+            # Auto fields are editable, so check for auto or non-editable pk.
+            self.form._meta.model._meta.auto_field or not self.form._meta.model._meta.pk.editable or
+            # Also search any parents for an auto field. (The pk info is
+            # propagated to child models so that does not need to be checked
+            # in parents.)
+            any(parent._meta.auto_field or not parent._meta.model._meta.pk.editable
+                for parent in self.form._meta.model._meta.get_parent_list())
         )
 
     def pk_field(self):

django/contrib/admin/options.py

@@ -841,13 +841,11 @@ def get_actions(self, request):
         actions = filter(None, actions)
 
         # Convert the actions into an OrderedDict keyed by name.
-        actions = OrderedDict(
+        return OrderedDict(
             (name, (func, name, desc))
             for func, name, desc in actions
         )
 
-        return actions
-
     def get_action_choices(self, request, default_choices=BLANK_CHOICE_DASH):
         """
         Return a list of choices for use in a form object.  Each choice is a

django/contrib/sessions/backends/base.py

@@ -151,8 +151,7 @@ def _get_new_session_key(self):
         while True:
             session_key = get_random_string(32, VALID_KEY_CHARS)
             if not self.exists(session_key):
-                break
-        return session_key
+                return session_key
 
     def _get_or_create_session_key(self):
         if self._session_key is None:

django/core/serializers/__init__.py

@@ -216,11 +216,7 @@ def sort_dependencies(app_list):
             # If all of the models in the dependency list are either already
             # on the final model list, or not on the original serialization list,
             # then we've found another model with all it's dependencies satisfied.
-            found = True
-            for candidate in ((d not in models or d in model_list) for d in deps):
-                if not candidate:
-                    found = False
-            if found:
+            if all(candidate for candidate in ((d not in models or d in model_list) for d in deps)):
                 model_list.append(model)
                 changed = True
             else:

django/db/migrations/autodetector.py

@@ -301,7 +301,7 @@ def _build_migration_list(self, graph=None):
                     if deps_satisfied:
                         chopped.append(operation)
                         dependencies.update(operation_dependencies)
-                        self.generated_operations[app_label] = self.generated_operations[app_label][1:]
+                        del self.generated_operations[app_label][0]
                     else:
                         break
                 # Make a migration! Well, only if there's stuff to put in it

django/db/migrations/graph.py

@@ -304,7 +304,7 @@ def root_nodes(self, app=None):
         """
         roots = set()
         for node in self.nodes:
-            if not any(key[0] == node[0] for key in self.node_map[node].parents) and (not app or app == node[0]):
+            if all(key[0] != node[0] for key in self.node_map[node].parents) and (not app or app == node[0]):
                 roots.add(node)
         return sorted(roots)
 
@@ -318,7 +318,7 @@ def leaf_nodes(self, app=None):
         """
         leaves = set()
         for node in self.nodes:
-            if not any(key[0] == node[0] for key in self.node_map[node].children) and (not app or app == node[0]):
+            if all(key[0] != node[0] for key in self.node_map[node].children) and (not app or app == node[0]):
                 leaves.add(node)
         return sorted(leaves)
 

django/db/models/fields/files.py

@@ -39,7 +39,7 @@ def _require_file(self):
 
     def _get_file(self):
         self._require_file()
-        if not hasattr(self, '_file') or self._file is None:
+        if getattr(self, '_file', None) is None:
             self._file = self.storage.open(self.name, 'rb')
         return self._file
 

django/dispatch/dispatcher.py

@@ -215,12 +215,10 @@ def _clear_dead_receivers(self):
         # Note: caller is assumed to hold self.lock.
         if self._dead_receivers:
             self._dead_receivers = False
-            new_receivers = []
-            for r in self.receivers:
-                if isinstance(r[1], weakref.ReferenceType) and r[1]() is None:
-                    continue
-                new_receivers.append(r)
-            self.receivers = new_receivers
+            self.receivers = [
+                r for r in self.receivers
+                if not(isinstance(r[1], weakref.ReferenceType) and r[1]() is None)
+            ]
 
     def _live_receivers(self, sender):
         """

django/test/runner.py

@@ -531,8 +531,7 @@ def build_suite(self, test_labels=None, extra_tests=None, **kwargs):
             # Since tests are distributed across processes on a per-TestCase
             # basis, there's no need for more processes than TestCases.
             parallel_units = len(parallel_suite.subsuites)
-            if self.parallel > parallel_units:
-                self.parallel = parallel_units
+            self.parallel = min(self.parallel, parallel_units)
 
             # If there's only one TestCase, parallelization isn't needed.
             if self.parallel > 1:

django/utils/synch.py

@@ -60,7 +60,7 @@ def reader(self):
     def writer_enters(self):
         with self.mutex:
             if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0:
-                self.active_writers += 1
+                self.active_writers = 1
                 self.can_write.release()
             else:
                 self.waiting_writers += 1

tests/auth_tests/test_context_processors.py

@@ -10,14 +10,10 @@
 
 class MockUser:
     def has_module_perms(self, perm):
-        if perm == 'mockapp':
-            return True
-        return False
+        return perm == 'mockapp'
 
     def has_perm(self, perm):
-        if perm == 'mockapp.someperm':
-            return True
-        return False
+        return perm == 'mockapp.someperm'
 
 
 class PermWrapperTests(SimpleTestCase):

tests/inspectdb/tests.py

@@ -189,7 +189,7 @@ def test_special_column_name_introspection(self):
                      table_name_filter=lambda tn: tn.startswith('inspectdb_special'),
                      stdout=out)
         output = out.getvalue()
-        base_name = 'Field' if not connection.features.uppercases_column_names else 'field'
+        base_name = 'field' if connection.features.uppercases_column_names else 'Field'
         self.assertIn("field = models.IntegerField()", output)
         self.assertIn("field_field = models.IntegerField(db_column='%s_')" % base_name, output)
         self.assertIn("field_field_0 = models.IntegerField(db_column='%s__')" % base_name, output)

tests/modeladmin/tests.py

@@ -671,27 +671,19 @@ class ModelAdminPermissionTests(SimpleTestCase):
 
     class MockUser:
         def has_module_perms(self, app_label):
-            if app_label == "modeladmin":
-                return True
-            return False
+            return app_label == 'modeladmin'
 
     class MockAddUser(MockUser):
         def has_perm(self, perm):
-            if perm == "modeladmin.add_band":
-                return True
-            return False
+            return perm == 'modeladmin.add_band'
 
     class MockChangeUser(MockUser):
         def has_perm(self, perm):
-            if perm == "modeladmin.change_band":
-                return True
-            return False
+            return perm == 'modeladmin.change_band'
 
     class MockDeleteUser(MockUser):
         def has_perm(self, perm):
-            if perm == "modeladmin.delete_band":
-                return True
-            return False
+            return perm == 'modeladmin.delete_band'
 
     def test_has_add_permission(self):
         """

tests/serializers/test_json.py

@@ -55,20 +55,13 @@ def _validate_output(serial_str):
 
     @staticmethod
     def _get_pk_values(serial_str):
-        ret_list = []
         serial_list = json.loads(serial_str)
-        for obj_dict in serial_list:
-            ret_list.append(obj_dict["pk"])
-        return ret_list
+        return [obj_dict['pk'] for obj_dict in serial_list]
 
     @staticmethod
     def _get_field_values(serial_str, field_name):
-        ret_list = []
         serial_list = json.loads(serial_str)
-        for obj_dict in serial_list:
-            if field_name in obj_dict["fields"]:
-                ret_list.append(obj_dict["fields"][field_name])
-        return ret_list
+        return [obj_dict['fields'][field_name] for obj_dict in serial_list if field_name in obj_dict['fields']]
 
     def test_indentation_whitespace(self):
         s = serializers.json.Serializer()