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
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.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.
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.
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.
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.
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.
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.
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:
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, _variables=None):
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
Fields.
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 Arguments.
graphene.Field(graphene.String, to=graphene.String())
# Is equivalent to:
graphene.Field(graphene.String, to=graphene.Argument(graphene.String))