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GraphQL

Starlette includes optional support for GraphQL, using the graphene library.

Here's an example of integrating the support into your application.

from starlette.applications import Starlette
from starlette.graphql import GraphQLApp
import graphene


class Query(graphene.ObjectType):
    hello = graphene.String(name=graphene.String(default_value="stranger"))

    def resolve_hello(self, info, name):
        return "Hello " + name


app = Starlette()
app.add_route('/', GraphQLApp(schema=graphene.Schema(query=Query)))

If you load up the page in a browser, you'll be served the GraphiQL tool, which you can use to interact with your GraphQL API.

GraphiQL

Accessing request information

The current request is available in the context.

class Query(graphene.ObjectType):
    user_agent = graphene.String()

    def resolve_user_agent(self, info):
        """
        Return the User-Agent of the incoming request.
        """
        request = info.context["request"]
        return request.headers.get("User-Agent", "<unknown>")

Adding background tasks

You can add background tasks to run once the response has been sent.

class Query(graphene.ObjectType):
    user_agent = graphene.String()

    def resolve_user_agent(self, info):
        """
        Return the User-Agent of the incoming request.
        """
        user_agent = request.headers.get("User-Agent", "<unknown>")
        background = info.context["background"]
        background.add_task(log_user_agent, user_agent=user_agent)
        return user_agent

async def log_user_agent(user_agent):
    ...

Sync or Async executors

If you're working with a standard ORM, then just use regular function calls for your "resolve" methods, and Starlette will manage running the GraphQL query within a seperate thread.

If you want to use an asyncronous ORM, then use "async resolve" methods, and make sure to setup Graphene's AsyncioExecutor using the executor argument.

from graphql.execution.executors.asyncio import AsyncioExecutor
from starlette.applications import Starlette
from starlette.graphql import GraphQLApp
import graphene


class Query(graphene.ObjectType):
    hello = graphene.String(name=graphene.String(default_value="stranger"))

    async def resolve_hello(self, info, name):
        # We can make asynchronous network calls here.
        return "Hello " + name


app = Starlette()

# We're using `executor_class=AsyncioExecutor` here.
app.add_route('/', GraphQLApp(schema=graphene.Schema(query=Query), executor_class=AsyncioExecutor))