Replaced temporary lists used for passing arguments with iterables.

django/contrib/admin/checks.py

@@ -87,10 +87,10 @@ class BaseModelAdminChecks:
         if not isinstance(obj.raw_id_fields, (list, tuple)):
             return must_be('a list or tuple', option='raw_id_fields', obj=obj, id='admin.E001')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_raw_id_fields_item(obj, obj.model, field_name, 'raw_id_fields[%d]' % index)
                 for index, field_name in enumerate(obj.raw_id_fields)
-            ]))
+            ))
 
     def _check_raw_id_fields_item(self, obj, model, field_name, label):
         """ Check an item of `raw_id_fields`, i.e. check that field named
@@ -136,10 +136,10 @@ class BaseModelAdminChecks:
                 )
             ]
 
-        return list(chain(*[
+        return list(chain.from_iterable(
             self._check_field_spec(obj, obj.model, field_name, 'fields')
             for field_name in obj.fields
-        ]))
+        ))
 
     def _check_fieldsets(self, obj):
         """ Check that fieldsets is properly formatted and doesn't contain
@@ -150,10 +150,10 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.fieldsets, (list, tuple)):
             return must_be('a list or tuple', option='fieldsets', obj=obj, id='admin.E007')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_fieldsets_item(obj, obj.model, fieldset, 'fieldsets[%d]' % index)
                 for index, fieldset in enumerate(obj.fieldsets)
-            ]))
+            ))
 
     def _check_fieldsets_item(self, obj, model, fieldset, label):
         """ Check an item of `fieldsets`, i.e. check that this is a pair of a
@@ -185,10 +185,10 @@ class BaseModelAdminChecks:
                     id='admin.E012',
                 )
             ]
-        return list(chain(*[
+        return list(chain.from_iterable(
             self._check_field_spec(obj, model, fieldset_fields, '%s[1]["fields"]' % label)
             for fieldset_fields in fieldset[1]['fields']
-        ]))
+        ))
 
     def _check_field_spec(self, obj, model, fields, label):
         """ `fields` should be an item of `fields` or an item of
@@ -196,10 +196,10 @@ class BaseModelAdminChecks:
         field name or a tuple of field names. """
 
         if isinstance(fields, tuple):
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_field_spec_item(obj, model, field_name, "%s[%d]" % (label, index))
                 for index, field_name in enumerate(fields)
-            ]))
+            ))
         else:
             return self._check_field_spec_item(obj, model, fields, label)
 
@@ -266,10 +266,10 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.filter_vertical, (list, tuple)):
             return must_be('a list or tuple', option='filter_vertical', obj=obj, id='admin.E017')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_filter_item(obj, obj.model, field_name, "filter_vertical[%d]" % index)
                 for index, field_name in enumerate(obj.filter_vertical)
-            ]))
+            ))
 
     def _check_filter_horizontal(self, obj):
         """ Check that filter_horizontal is a sequence of field names. """
@@ -279,10 +279,10 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.filter_horizontal, (list, tuple)):
             return must_be('a list or tuple', option='filter_horizontal', obj=obj, id='admin.E018')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_filter_item(obj, obj.model, field_name, "filter_horizontal[%d]" % index)
                 for index, field_name in enumerate(obj.filter_horizontal)
-            ]))
+            ))
 
     def _check_filter_item(self, obj, model, field_name, label):
         """ Check one item of `filter_vertical` or `filter_horizontal`, i.e.
@@ -307,11 +307,11 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.radio_fields, dict):
             return must_be('a dictionary', option='radio_fields', obj=obj, id='admin.E021')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_radio_fields_key(obj, obj.model, field_name, 'radio_fields') +
                 self._check_radio_fields_value(obj, val, 'radio_fields["%s"]' % field_name)
                 for field_name, val in obj.radio_fields.items()
-            ]))
+            ))
 
     def _check_radio_fields_key(self, obj, model, field_name, label):
         """ Check that a key of `radio_fields` dictionary is name of existing
@@ -377,11 +377,11 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.prepopulated_fields, dict):
             return must_be('a dictionary', option='prepopulated_fields', obj=obj, id='admin.E026')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_prepopulated_fields_key(obj, obj.model, field_name, 'prepopulated_fields') +
                 self._check_prepopulated_fields_value(obj, obj.model, val, 'prepopulated_fields["%s"]' % field_name)
                 for field_name, val in obj.prepopulated_fields.items()
-            ]))
+            ))
 
     def _check_prepopulated_fields_key(self, obj, model, field_name, label):
         """ Check a key of `prepopulated_fields` dictionary, i.e. check that it
@@ -413,10 +413,10 @@ class BaseModelAdminChecks:
         if not isinstance(val, (list, tuple)):
             return must_be('a list or tuple', option=label, obj=obj, id='admin.E029')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_prepopulated_fields_value_item(obj, model, subfield_name, "%s[%r]" % (label, index))
                 for index, subfield_name in enumerate(val)
-            ]))
+            ))
 
     def _check_prepopulated_fields_value_item(self, obj, model, field_name, label):
         """ For `prepopulated_fields` equal to {"slug": ("title",)},
@@ -438,10 +438,10 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.ordering, (list, tuple)):
             return must_be('a list or tuple', option='ordering', obj=obj, id='admin.E031')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_ordering_item(obj, obj.model, field_name, 'ordering[%d]' % index)
                 for index, field_name in enumerate(obj.ordering)
-            ]))
+            ))
 
     def _check_ordering_item(self, obj, model, field_name, label):
         """ Check that `ordering` refers to existing fields. """
@@ -482,10 +482,10 @@ class BaseModelAdminChecks:
         elif not isinstance(obj.readonly_fields, (list, tuple)):
             return must_be('a list or tuple', option='readonly_fields', obj=obj, id='admin.E034')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_readonly_fields_item(obj, obj.model, field_name, "readonly_fields[%d]" % index)
                 for index, field_name in enumerate(obj.readonly_fields)
-            ]))
+            ))
 
     def _check_readonly_fields_item(self, obj, model, field_name, label):
         if callable(field_name):
@@ -553,10 +553,10 @@ class ModelAdminChecks(BaseModelAdminChecks):
         if not isinstance(obj.inlines, (list, tuple)):
             return must_be('a list or tuple', option='inlines', obj=obj, id='admin.E103')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_inlines_item(obj, obj.model, item, "inlines[%d]" % index)
                 for index, item in enumerate(obj.inlines)
-            ]))
+            ))
 
     def _check_inlines_item(self, obj, model, inline, label):
         """ Check one inline model admin. """
@@ -592,10 +592,10 @@ class ModelAdminChecks(BaseModelAdminChecks):
         if not isinstance(obj.list_display, (list, tuple)):
             return must_be('a list or tuple', option='list_display', obj=obj, id='admin.E107')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_list_display_item(obj, obj.model, item, "list_display[%d]" % index)
                 for index, item in enumerate(obj.list_display)
-            ]))
+            ))
 
     def _check_list_display_item(self, obj, model, item, label):
         if callable(item):
@@ -663,10 +663,10 @@ class ModelAdminChecks(BaseModelAdminChecks):
             return must_be('a list, a tuple, or None', option='list_display_links', obj=obj, id='admin.E110')
         # Check only if ModelAdmin.get_list_display() isn't overridden.
         elif obj.get_list_display.__func__ is ModelAdmin.get_list_display:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_list_display_links_item(obj, field_name, "list_display_links[%d]" % index)
                 for index, field_name in enumerate(obj.list_display_links)
-            ]))
+            ))
         return []
 
     def _check_list_display_links_item(self, obj, field_name, label):
@@ -687,10 +687,10 @@ class ModelAdminChecks(BaseModelAdminChecks):
         if not isinstance(obj.list_filter, (list, tuple)):
             return must_be('a list or tuple', option='list_filter', obj=obj, id='admin.E112')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_list_filter_item(obj, obj.model, item, "list_filter[%d]" % index)
                 for index, item in enumerate(obj.list_filter)
-            ]))
+            ))
 
     def _check_list_filter_item(self, obj, model, item, label):
         """
@@ -775,10 +775,10 @@ class ModelAdminChecks(BaseModelAdminChecks):
         if not isinstance(obj.list_editable, (list, tuple)):
             return must_be('a list or tuple', option='list_editable', obj=obj, id='admin.E120')
         else:
-            return list(chain(*[
+            return list(chain.from_iterable(
                 self._check_list_editable_item(obj, obj.model, item, "list_editable[%d]" % index)
                 for index, item in enumerate(obj.list_editable)
-            ]))
+            ))
 
     def _check_list_editable_item(self, obj, model, field_name, label):
         try:

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