.. _Scalars: Scalars ======= Scalar types represent concrete values at the leaves of a query. There are several built in types that Graphene provides out of the box which represent common values in Python. You can also create your own Scalar types to better express values that you might have in your data model. All Scalar types accept the following arguments. All are optional: ``name``: *string* Override the name of the Field. ``description``: *string* A description of the type to show in the GraphiQL browser. ``required``: *boolean* If ``True``, the server will enforce a value for this field. See `NonNull <../list-and-nonnull.html#nonnull>`_. Default is ``False``. ``deprecation_reason``: *string* Provide a deprecation reason for the Field. ``default_value``: *any* Provide a default value for the Field. Built in scalars ---------------- Graphene defines the following base Scalar Types that match the default `GraphQL types `_: ``graphene.String`` ^^^^^^^^^^^^^^^^^^^ Represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text. ``graphene.Int`` ^^^^^^^^^^^^^^^^ Represents non-fractional signed whole numeric values. Int is a signed 32‐bit integer per the `GraphQL spec `_ ``graphene.Float`` ^^^^^^^^^^^^^^^^^^ Represents signed double-precision fractional values as specified by `IEEE 754 `_. ``graphene.Boolean`` ^^^^^^^^^^^^^^^^^^^^ Represents `true` or `false`. ``graphene.ID`` ^^^^^^^^^^^^^^^ Represents a unique identifier, often used to refetch an object or as key for a cache. The ID type appears in a JSON response as a String; however, it is not intended to be human-readable. When expected as an input type, any string (such as `"4"`) or integer (such as `4`) input value will be accepted as an ID. ---- Graphene also provides custom scalars for common values: ``graphene.Date`` ^^^^^^^^^^^^^^^^^ Represents a Date value as specified by `iso8601 `_. .. code:: python import datetime from graphene import Schema, ObjectType, Date class Query(ObjectType): one_week_from = Date(required=True, date_input=Date(required=True)) def resolve_one_week_from(root, info, date_input): assert date_input == datetime.date(2006, 1, 2) return date_input + datetime.timedelta(weeks=1) schema = Schema(query=Query) results = schema.execute(""" query { oneWeekFrom(dateInput: "2006-01-02") } """) assert results.data == {"oneWeekFrom": "2006-01-09"} ``graphene.DateTime`` ^^^^^^^^^^^^^^^^^^^^^ Represents a DateTime value as specified by `iso8601 `_. .. code:: python import datetime from graphene import Schema, ObjectType, DateTime class Query(ObjectType): one_hour_from = DateTime(required=True, datetime_input=DateTime(required=True)) def resolve_one_hour_from(root, info, datetime_input): assert datetime_input == datetime.datetime(2006, 1, 2, 15, 4, 5) return datetime_input + datetime.timedelta(hours=1) schema = Schema(query=Query) results = schema.execute(""" query { oneHourFrom(datetimeInput: "2006-01-02T15:04:05") } """) assert results.data == {"oneHourFrom": "2006-01-02T16:04:05"} ``graphene.Time`` ^^^^^^^^^^^^^^^^^ Represents a Time value as specified by `iso8601 `_. .. code:: python import datetime from graphene import Schema, ObjectType, Time class Query(ObjectType): one_hour_from = Time(required=True, time_input=Time(required=True)) def resolve_one_hour_from(root, info, time_input): assert time_input == datetime.time(15, 4, 5) tmp_time_input = datetime.datetime.combine(datetime.date(1, 1, 1), time_input) return (tmp_time_input + datetime.timedelta(hours=1)).time() schema = Schema(query=Query) results = schema.execute(""" query { oneHourFrom(timeInput: "15:04:05") } """) assert results.data == {"oneHourFrom": "16:04:05"} ``graphene.Decimal`` ^^^^^^^^^^^^^^^^^^^^ Represents a Python Decimal value. .. code:: python import decimal from graphene import Schema, ObjectType, Decimal class Query(ObjectType): add_one_to = Decimal(required=True, decimal_input=Decimal(required=True)) def resolve_add_one_to(root, info, decimal_input): assert decimal_input == decimal.Decimal("10.50") return decimal_input + decimal.Decimal("1") schema = Schema(query=Query) results = schema.execute(""" query { addOneTo(decimalInput: "10.50") } """) assert results.data == {"addOneTo": "11.50"} ``graphene.JSONString`` ^^^^^^^^^^^^^^^^^^^^^^^ Represents a JSON string. .. code:: python from graphene import Schema, ObjectType, JSONString, String class Query(ObjectType): update_json_key = JSONString( required=True, json_input=JSONString(required=True), key=String(required=True), value=String(required=True) ) def resolve_update_json_key(root, info, json_input, key, value): assert json_input == {"name": "Jane"} json_input[key] = value return json_input schema = Schema(query=Query) results = schema.execute(""" query { updateJsonKey(jsonInput: "{\\"name\\": \\"Jane\\"}", key: "name", value: "Beth") } """) assert results.data == {"updateJsonKey": "{\"name\": \"Beth\"}"} ``graphene.Base64`` ^^^^^^^^^^^^^^^^^^^ Represents a Base64 encoded string. .. code:: python from graphene import Schema, ObjectType, Base64 class Query(ObjectType): increment_encoded_id = Base64( required=True, base64_input=Base64(required=True), ) def resolve_increment_encoded_id(root, info, base64_input): assert base64_input == "4" return int(base64_input) + 1 schema = Schema(query=Query) results = schema.execute(""" query { incrementEncodedId(base64Input: "NA==") } """) assert results.data == {"incrementEncodedId": "NQ=="} Custom scalars -------------- You can create custom scalars for your schema. The following is an example for creating a DateTime scalar: .. code:: python import datetime from graphene.types import Scalar from graphql.language import ast class DateTime(Scalar): '''DateTime Scalar Description''' @staticmethod def serialize(dt): return dt.isoformat() @staticmethod def parse_literal(node): if isinstance(node, ast.StringValue): return datetime.datetime.strptime( node.value, "%Y-%m-%dT%H:%M:%S.%f") @staticmethod def parse_value(value): return datetime.datetime.strptime(value, "%Y-%m-%dT%H:%M:%S.%f") Mounting Scalars ---------------- Scalars mounted in a ``ObjectType``, ``Interface`` or ``Mutation`` act as ``Field``\ s. .. code:: python class Person(graphene.ObjectType): name = graphene.String() # Is equivalent to: class Person(graphene.ObjectType): name = graphene.Field(graphene.String) **Note:** when using the ``Field`` constructor directly, pass the type and not an instance. Types mounted in a ``Field`` act as ``Argument``\ s. .. code:: python graphene.Field(graphene.String, to=graphene.String()) # Is equivalent to: graphene.Field(graphene.String, to=graphene.Argument(graphene.String))