Avoided creation of temporary sets.

django/contrib/admin/views/main.py

@@ -268,7 +268,7 @@ class ChangeList:
         # ordering fields so we can guarantee a deterministic order across all
         # database backends.
         pk_name = self.lookup_opts.pk.name
-        if not (set(ordering) & {'pk', '-pk', pk_name, '-' + pk_name}):
+        if {'pk', '-pk', pk_name, '-' + pk_name}.isdisjoint(ordering):
             # The two sets do not intersect, meaning the pk isn't present. So
             # we add it.
             ordering.append('-pk')

django/contrib/sessions/backends/file.py

@@ -52,7 +52,7 @@ class SessionStore(SessionBase):
         # Make sure we're not vulnerable to directory traversal. Session keys
         # should always be md5s, so they should never contain directory
         # components.
-        if not set(session_key).issubset(set(VALID_KEY_CHARS)):
+        if not set(session_key).issubset(VALID_KEY_CHARS):
             raise InvalidSessionKey(
                 "Invalid characters in session key")
 

django/core/checks/registry.py

@@ -67,7 +67,7 @@ class CheckRegistry:
 
         if tags is not None:
             checks = [check for check in checks
-                      if hasattr(check, 'tags') and set(check.tags) & set(tags)]
+                      if hasattr(check, 'tags') and not set(check.tags).isdisjoint(tags)]
         else:
             # By default, 'database'-tagged checks are not run as they do more
             # than mere static code analysis.

django/core/management/__init__.py

@@ -122,7 +122,7 @@ def call_command(command_name, *args, **options):
     # Raise an error if any unknown options were passed.
     stealth_options = set(command.base_stealth_options + command.stealth_options)
     dest_parameters = {action.dest for action in parser._actions}
-    valid_options = dest_parameters | stealth_options | set(opt_mapping)
+    valid_options = (dest_parameters | stealth_options).union(opt_mapping)
     unknown_options = set(options) - valid_options
     if unknown_options:
         raise TypeError(

django/core/management/commands/compilemessages.py

@@ -85,7 +85,7 @@ class Command(BaseCommand):
 
         # Account for excluded locales
         locales = locale or all_locales
-        locales = set(locales) - set(exclude)
+        locales = set(locales).difference(exclude)
 
         for basedir in basedirs:
             if locales:

django/core/management/commands/makemessages.py

@@ -371,7 +371,7 @@ class Command(BaseCommand):
             locales = all_locales
         else:
             locales = locale or all_locales
-            locales = set(locales) - set(exclude)
+            locales = set(locales).difference(exclude)
 
         if locales:
             check_programs('msguniq', 'msgmerge', 'msgattrib')

django/db/migrations/autodetector.py

@@ -451,12 +451,12 @@ class MigrationAutodetector:
         """
         self.renamed_models = {}
         self.renamed_models_rel = {}
-        added_models = set(self.new_model_keys) - set(self.old_model_keys)
+        added_models = set(self.new_model_keys).difference(self.old_model_keys)
         for app_label, model_name in sorted(added_models):
             model_state = self.to_state.models[app_label, model_name]
             model_fields_def = self.only_relation_agnostic_fields(model_state.fields)
 
-            removed_models = set(self.old_model_keys) - set(self.new_model_keys)
+            removed_models = set(self.old_model_keys).difference(self.new_model_keys)
             for rem_app_label, rem_model_name in removed_models:
                 if rem_app_label == app_label:
                     rem_model_state = self.from_state.models[rem_app_label, rem_model_name]
@@ -642,7 +642,7 @@ class MigrationAutodetector:
         models it's safe to skip all the pointless field stuff and just chuck
         out an operation.
         """
-        added = set(self.new_proxy_keys) - set(self.old_proxy_keys)
+        added = set(self.new_proxy_keys).difference(self.old_proxy_keys)
         for app_label, model_name in sorted(added):
             model_state = self.to_state.models[app_label, model_name]
             assert model_state.options.get("proxy")
@@ -764,7 +764,7 @@ class MigrationAutodetector:
 
     def generate_deleted_proxies(self):
         """Make DeleteModel options for proxy models."""
-        deleted = set(self.old_proxy_keys) - set(self.new_proxy_keys)
+        deleted = set(self.old_proxy_keys).difference(self.new_proxy_keys)
         for app_label, model_name in sorted(deleted):
             model_state = self.from_state.models[app_label, model_name]
             assert model_state.options.get("proxy")

django/db/models/fields/related_descriptors.py

@@ -1044,7 +1044,7 @@ def create_forward_many_to_many_manager(superclass, rel, reverse):
                             source_field_name: self.related_val[0],
                             '%s__in' % target_field_name: new_ids,
                         }))
-                new_ids = new_ids - set(vals)
+                new_ids.difference_update(vals)
 
                 with transaction.atomic(using=db, savepoint=False):
                     if self.reverse or source_field_name == self.source_field_name:

django/db/models/sql/query.py

@@ -789,7 +789,7 @@ class Query:
         relabelling any references to them in select columns and the where
         clause.
         """
-        assert set(change_map).intersection(set(change_map.values())) == set()
+        assert set(change_map).isdisjoint(change_map.values())
 
         # 1. Update references in "select" (normal columns plus aliases),
         # "group by" and "where".
@@ -975,7 +975,7 @@ class Query:
 
     def prepare_lookup_value(self, value, lookups, can_reuse, allow_joins=True):
         # Default lookup if none given is exact.
-        used_joins = []
+        used_joins = set()
         if len(lookups) == 0:
             lookups = ['exact']
         # Interpret '__exact=None' as the sql 'is NULL'; otherwise, reject all
@@ -987,12 +987,11 @@ class Query:
         elif hasattr(value, 'resolve_expression'):
             pre_joins = self.alias_refcount.copy()
             value = value.resolve_expression(self, reuse=can_reuse, allow_joins=allow_joins)
-            used_joins = [k for k, v in self.alias_refcount.items() if v > pre_joins.get(k, 0)]
+            used_joins = {k for k, v in self.alias_refcount.items() if v > pre_joins.get(k, 0)}
         elif isinstance(value, (list, tuple)):
             # The items of the iterable may be expressions and therefore need
             # to be resolved independently.
             processed_values = []
-            used_joins = set()
             for sub_value in value:
                 if hasattr(sub_value, 'resolve_expression'):
                     pre_joins = self.alias_refcount.copy()
@@ -1172,7 +1171,7 @@ class Query:
 
         # Update used_joins before trimming since they are reused to determine
         # which joins could be later promoted to INNER.
-        used_joins = set(used_joins).union(set(join_list))
+        used_joins.update(join_list)
         targets, alias, join_list = self.trim_joins(sources, join_list, path)
         if can_reuse is not None:
             can_reuse.update(join_list)

django/forms/models.py

@@ -258,8 +258,8 @@ class ModelFormMetaclass(DeclarativeFieldsMetaclass):
             )
 
             # make sure opts.fields doesn't specify an invalid field
-            none_model_fields = [k for k, v in fields.items() if not v]
+            none_model_fields = {k for k, v in fields.items() if not v}
-            missing_fields = set(none_model_fields) - set(new_class.declared_fields)
+            missing_fields = none_model_fields.difference(new_class.declared_fields)
             if missing_fields:
                 message = 'Unknown field(s) (%s) specified for %s'
                 message = message % (', '.join(missing_fields),
@@ -682,8 +682,8 @@ class BaseModelFormSet(BaseFormSet):
         for form in valid_forms:
             exclude = form._get_validation_exclusions()
             unique_checks, date_checks = form.instance._get_unique_checks(exclude=exclude)
-            all_unique_checks = all_unique_checks.union(set(unique_checks))
+            all_unique_checks.update(unique_checks)
-            all_date_checks = all_date_checks.union(set(date_checks))
+            all_date_checks.update(date_checks)
 
         errors = []
         # Do each of the unique checks (unique and unique_together)

django/urls/resolvers.py

@@ -436,7 +436,7 @@ class RegexURLResolver(LocaleRegexProvider):
                         continue
                     candidate_subs = dict(zip(params, text_args))
                 else:
-                    if set(kwargs) | set(defaults) != set(params) | set(defaults):
+                    if set(kwargs).symmetric_difference(params).difference(defaults):
                         continue
                     matches = True
                     for k, v in defaults.items():