Perfer iter(dict) over iter(dict.keys()) (#5736)

Calling dict.keys() is unnecessary. The two are functionally equivalent
on modern Pythons.

Inspired by Lennart Regebro's talk "Prehistoric Patterns in Python" from
PyCon 2017.

https://www.youtube.com/watch?v=V5-JH23Vk0I

Author: jdufresne

docs/api-guide/serializers.md

@@ -1083,7 +1083,7 @@ For example, if you wanted to be able to set which fields should be used by a se
             if fields is not None:
                 # Drop any fields that are not specified in the `fields` argument.
                 allowed = set(fields)
-                existing = set(self.fields.keys())
+                existing = set(self.fields)
                 for field_name in existing - allowed:
                     self.fields.pop(field_name)
 

rest_framework/fields.py

@@ -1420,7 +1420,7 @@ def _set_choices(self, choices):
         # Allows us to deal with eg. integer choices while supporting either
         # integer or string input, but still get the correct datatype out.
         self.choice_strings_to_values = {
-            six.text_type(key): key for key in self.choices.keys()
+            six.text_type(key): key for key in self.choices
         }
 
     choices = property(_get_choices, _set_choices)

rest_framework/filters.py

@@ -218,7 +218,7 @@ def get_valid_fields(self, queryset, view, context={}):
             ]
             valid_fields += [
                 (key, key.title().split('__'))
-                for key in queryset.query.annotations.keys()
+                for key in queryset.query.annotations
             ]
         else:
             valid_fields = [

rest_framework/relations.py

@@ -133,7 +133,7 @@ def many_init(cls, *args, **kwargs):
             return CustomManyRelatedField(*args, **kwargs)
         """
         list_kwargs = {'child_relation': cls(*args, **kwargs)}
-        for key in kwargs.keys():
+        for key in kwargs:
             if key in MANY_RELATION_KWARGS:
                 list_kwargs[key] = kwargs[key]
         return ManyRelatedField(**list_kwargs)

rest_framework/renderers.py

@@ -805,8 +805,8 @@ def get_context(self, data, accepted_media_type, renderer_context):
             header = results
             style = 'detail'
 
-        columns = [key for key in header.keys() if key != 'url']
-        details = [key for key in header.keys() if key != 'url']
+        columns = [key for key in header if key != 'url']
+        details = [key for key in header if key != 'url']
 
         context['style'] = style
         context['columns'] = columns

rest_framework/schemas/generators.py

@@ -228,7 +228,7 @@ def get_allowed_methods(self, callback):
         Return a list of the valid HTTP methods for this endpoint.
         """
         if hasattr(callback, 'actions'):
-            actions = set(callback.actions.keys())
+            actions = set(callback.actions)
             http_method_names = set(callback.cls.http_method_names)
             methods = [method.upper() for method in actions & http_method_names]
         else:

rest_framework/schemas/inspectors.py

@@ -54,13 +54,13 @@ def field_to_schema(field):
         return coreschema.String(title=title, description=description)
     elif isinstance(field, serializers.MultipleChoiceField):
         return coreschema.Array(
-            items=coreschema.Enum(enum=list(field.choices.keys())),
+            items=coreschema.Enum(enum=list(field.choices)),
             title=title,
             description=description
         )
     elif isinstance(field, serializers.ChoiceField):
         return coreschema.Enum(
-            enum=list(field.choices.keys()),
+            enum=list(field.choices),
             title=title,
             description=description
         )

rest_framework/serializers.py

@@ -1136,9 +1136,9 @@ def get_default_field_names(self, declared_fields, model_info):
         """
         return (
             [model_info.pk.name] +
-            list(declared_fields.keys()) +
-            list(model_info.fields.keys()) +
-            list(model_info.forward_relations.keys())
+            list(declared_fields) +
+            list(model_info.fields) +
+            list(model_info.forward_relations)
         )
 
     # Methods for constructing serializer fields...
@@ -1194,7 +1194,7 @@ def build_standard_field(self, field_name, model_field):
                 'error_messages', 'validators', 'allow_null', 'allow_blank',
                 'choices'
             }
-            for key in list(field_kwargs.keys()):
+            for key in list(field_kwargs):
                 if key not in valid_kwargs:
                     field_kwargs.pop(key)
 
@@ -1364,7 +1364,7 @@ def get_uniqueness_extra_kwargs(self, field_names, declared_fields, extra_kwargs
 
         # Include each of the `unique_together` field names,
         # so long as all the field names are included on the serializer.
-        for parent_class in [model] + list(model._meta.parents.keys()):
+        for parent_class in [model] + list(model._meta.parents):
             for unique_together_list in parent_class._meta.unique_together:
                 if set(field_names).issuperset(set(unique_together_list)):
                     unique_constraint_names |= set(unique_together_list)
@@ -1466,7 +1466,7 @@ def get_unique_together_validators(self):
         """
         model_class_inheritance_tree = (
             [self.Meta.model] +
-            list(self.Meta.model._meta.parents.keys())
+            list(self.Meta.model._meta.parents)
         )
 
         # The field names we're passing though here only include fields
@@ -1566,9 +1566,9 @@ def get_default_field_names(self, declared_fields, model_info):
         """
         return (
             [self.url_field_name] +
-            list(declared_fields.keys()) +
-            list(model_info.fields.keys()) +
-            list(model_info.forward_relations.keys())
+            list(declared_fields) +
+            list(model_info.fields) +
+            list(model_info.forward_relations)
         )
 
     def build_nested_field(self, field_name, relation_info, nested_depth):

rest_framework/test.py

@@ -175,7 +175,7 @@ def _encode_data(self, data, format=None, content_type=None):
                 "Set TEST_REQUEST_RENDERER_CLASSES to enable "
                 "extra request formats.".format(
                     format,
-                    ', '.join(["'" + fmt + "'" for fmt in self.renderer_classes.keys()])
+                    ', '.join(["'" + fmt + "'" for fmt in self.renderer_classes])
                 )
             )
 

rest_framework/utils/html.py

@@ -59,7 +59,7 @@ def parse_html_list(dictionary, prefix=''):
             ret[index][key] = value
         else:
             ret[index] = MultiValueDict({key: [value]})
-    return [ret[item] for item in sorted(ret.keys())]
+    return [ret[item] for item in sorted(ret)]
 
 
 def parse_html_dict(dictionary, prefix=''):

rest_framework/utils/mediatypes.py

@@ -55,7 +55,7 @@ def __init__(self, media_type_str):
 
     def match(self, other):
         """Return true if this MediaType satisfies the given MediaType."""
-        for key in self.params.keys():
+        for key in self.params:
             if key != 'q' and other.params.get(key, None) != self.params.get(key, None):
                 return False
 
@@ -76,7 +76,7 @@ def precedence(self):
             return 0
         elif self.sub_type == '*':
             return 1
-        elif not self.params or list(self.params.keys()) == ['q']:
+        elif not self.params or list(self.params) == ['q']:
             return 2
         return 3
 

tests/test_bound_fields.py

@@ -54,7 +54,7 @@ class ExampleSerializer(serializers.Serializer):
 
         serializer = ExampleSerializer()
         del serializer.fields['text']
-        assert 'text' not in serializer.fields.keys()
+        assert 'text' not in serializer.fields
 
     def test_as_form_fields(self):
         class ExampleSerializer(serializers.Serializer):

tests/test_fields.py

@@ -401,15 +401,15 @@ class TestSerializer(serializers.Serializer):
 
         serializer = TestSerializer(data=QueryDict('message='))
         assert serializer.is_valid()
-        assert list(serializer.validated_data.keys()) == ['message']
+        assert list(serializer.validated_data) == ['message']
 
     def test_empty_html_uuidfield_with_optional(self):
         class TestSerializer(serializers.Serializer):
             message = serializers.UUIDField(required=False)
 
         serializer = TestSerializer(data=QueryDict('message='))
         assert serializer.is_valid()
-        assert list(serializer.validated_data.keys()) == []
+        assert list(serializer.validated_data) == []
 
     def test_empty_html_charfield_allow_null(self):
         class TestSerializer(serializers.Serializer):

tests/test_metadata.py

@@ -207,7 +207,7 @@ def check_permissions(self, request):
         view = ExampleView.as_view()
         response = view(request=request)
         assert response.status_code == status.HTTP_200_OK
-        assert list(response.data['actions'].keys()) == ['PUT']
+        assert list(response.data['actions']) == ['PUT']
 
     def test_object_permissions(self):
         """

tests/test_multitable_inheritance.py

@@ -44,7 +44,7 @@ def test_multitable_inherited_model_fields_as_expected(self):
         """
         child = ChildModel(name1='parent name', name2='child name')
         serializer = DerivedModelSerializer(child)
-        assert set(serializer.data.keys()) == {'name1', 'name2', 'id'}
+        assert set(serializer.data) == {'name1', 'name2', 'id'}
 
     def test_onetoone_primary_key_model_fields_as_expected(self):
         """
@@ -54,7 +54,7 @@ def test_onetoone_primary_key_model_fields_as_expected(self):
         parent = ParentModel.objects.create(name1='parent name')
         associate = AssociatedModel.objects.create(name='hello', ref=parent)
         serializer = AssociatedModelSerializer(associate)
-        assert set(serializer.data.keys()) == {'name', 'ref'}
+        assert set(serializer.data) == {'name', 'ref'}
 
     def test_data_is_valid_without_parent_ptr(self):
         """

tests/test_one_to_one_with_inheritance.py

@@ -39,5 +39,5 @@ def test_multitable_inherited_model_fields_as_expected(self):
         """
         child = ChildModel(name1='parent name', name2='child name')
         serializer = DerivedModelSerializer(child)
-        self.assertEqual(set(serializer.data.keys()),
+        self.assertEqual(set(serializer.data),
                          {'name1', 'name2', 'id', 'childassociatedmodel'})

tests/test_permissions.py

@@ -151,7 +151,7 @@ def test_options_permitted(self):
         response = root_view(request, pk='1')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertIn('actions', response.data)
-        self.assertEqual(list(response.data['actions'].keys()), ['POST'])
+        self.assertEqual(list(response.data['actions']), ['POST'])
 
         request = factory.options(
             '/1',
@@ -160,7 +160,7 @@ def test_options_permitted(self):
         response = instance_view(request, pk='1')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertIn('actions', response.data)
-        self.assertEqual(list(response.data['actions'].keys()), ['PUT'])
+        self.assertEqual(list(response.data['actions']), ['PUT'])
 
     def test_options_disallowed(self):
         request = factory.options(
@@ -195,7 +195,7 @@ def test_options_updateonly(self):
         response = instance_view(request, pk='1')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertIn('actions', response.data)
-        self.assertEqual(list(response.data['actions'].keys()), ['PUT'])
+        self.assertEqual(list(response.data['actions']), ['PUT'])
 
     def test_empty_view_does_not_assert(self):
         request = factory.get('/1', HTTP_AUTHORIZATION=self.permitted_credentials)

tests/test_request.py

@@ -103,8 +103,8 @@ def test_request_POST_with_files(self):
         upload = SimpleUploadedFile("file.txt", b"file_content")
         request = Request(factory.post('/', {'upload': upload}))
         request.parsers = (FormParser(), MultiPartParser())
-        assert list(request.POST.keys()) == []
-        assert list(request.FILES.keys()) == ['upload']
+        assert list(request.POST) == []
+        assert list(request.FILES) == ['upload']
 
     def test_standard_behaviour_determines_form_content_PUT(self):
         """

tests/test_serializer_lists.py

@@ -15,7 +15,7 @@ def __init__(self, **kwargs):
     def __eq__(self, other):
         if self._data.keys() != other._data.keys():
             return False
-        for key in self._data.keys():
+        for key in self._data:
             if self._data[key] != other._data[key]:
                 return False
         return True