Example graphql server

server.py

import uvicorn
from graphene import (
    ObjectType,
    String,
    Schema,
    AbstractType,
    Field,
    Int,
    List,
    Mutation,
    Boolean,
)
from starlette.applications import Starlette
from starlette.routing import Route
from starlette.graphql import GraphQLApp

DATABASE = {
    "users": [{"id": 1, "name": "Bachmann"}, {"id": 2, "name": "Rachel"}],
    "connections": [
        {"id": 1, "user_id": 1, "friend_id": 2},
        {"id": 2, "user_id": 2, "friend_id": 1},
    ],
    "posts": [{"id": 1, "author_id": 1, "content": "Hello World!"}],
    "comments": [{"id": 1, "post_id": 1, "author_id": 2, "comment": "Bit cliche..."}],
}


def _find_by_field(field, field_value, table):
    for row in table:
        if row[field] == field_value:
            return row
    raise ValueError("Not Found")


def _find_by_id(value, table):
    return _find_by_field("id", value, table)


class User(ObjectType):
    id = String()
    name = String()
    connections = List(lambda: Connection)

    def resolve_connections(parent, info):
        return [
            connection
            for connection in DATABASE["connections"]
            if connection["user_id"] == parent["id"]
        ]


class Connection(ObjectType):
    id = String()
    user = Field(User)
    friend = Field(User)

    def resolve_user(parent, info):
        return _find_by_id(parent["user_id"], DATABASE["users"])

    def resolve_friend(parent, info):
        return _find_by_id(parent["friend_id"], DATABASE["users"])


class Post(ObjectType):
    id = String()
    author = Field(User)
    content = String()
    comments = List(lambda: Comment)

    def resolve_author(parent, info):
        return _find_by_id(parent["author_id"], DATABASE["users"])

    def resolve_comments(parent, info):
        return [
            comment
            for comment in DATABASE["comments"]
            if comment["post_id"] == parent["id"]
        ]


class Comment(ObjectType):
    id = String()
    post = Field(Post)
    author = Field(User)
    comment = String()

    def resolve_post(parent, info):
        return _find_by_field(parent["post_id"], DATABASE["posts"])

    def resolve_author(parent, info):
        return _find_by_id(parent["author_id"], DATABASE["users"])


class CommentQuery(AbstractType):
    comments = List(Comment, post_id=Int())

    def resolve_comments(parent, info, post_id):
        return [
            comment for comment in DATABASE["comments"] if comment["post_id"] == post_id
        ]


class PostQuery(AbstractType):
    post = Field(Post, author_id=Int())

    def resolve_post(parent, info, author_id):
        return _find_by_field("author_id", author_id, DATABASE["posts"])


class ConnectionQuery(AbstractType):
    connection = Field(Connection, user_id=Int())

    def resolve_connection(parent, info, user_id):
        return _find_by_field("user_id", user_id, DATABASE["connections"])


class UserQuery(AbstractType):
    user = Field(User, user_id=Int())

    def resolve_user(parent, info, user_id):
        return _find_by_id(user_id, DATABASE["users"])


class CreatePost(Mutation):
    class Arguments:
        user_id = String()
        post_content = String()

    ok = Boolean()
    post = Field(lambda: Post)

    def mutate(root, info, user_id, post_content):
        post = {
            "id": max([post["id"] for post in DATABASE["posts"]]) + 1,
            "author_id": user_id,
            "content": post_content,
        }
        DATABASE["posts"].append(post)
        ok = True
        return CreatePost(post=post, ok=ok)


class PostMutations(AbstractType):
    create_post = CreatePost.Field()


class Mutations(PostMutations, ObjectType):
    pass


class Query(UserQuery, ConnectionQuery, PostQuery, CommentQuery, ObjectType):
    pass


schema = Schema(query=Query, mutation=Mutations)
routes = [Route("/graphql", GraphQLApp(schema=schema))]

app = Starlette(routes=routes)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

venv ❯ pip freeze
aniso8601==7.0.0
click==7.1.1
graphene==2.1.8
graphql-core==2.3.1
graphql-relay==2.0.1
h11==0.9.0
httptools==0.1.1
promise==2.3
Rx==1.6.1
six==1.14.0
starlette==0.13.3
uvicorn==0.11.3
uvloop==0.14.0
websockets==8.1