Skip to content

2022-05-30 API

Graphene GraphQL Library for Python

Graphene GraphQL Library for Python#

What is GraphQL?#

  • GraphQL is a query language for your API, and a server-side runtime for executing queries using a type system you define for your data
  • A GraphQL service defines types and fields on those types - then functions for each type on each field

A graphQL service that tells you who the logged in user is and the username of that user:

type Query {
  me: User
}

type User {
  id: ID
  name: String
}

Along with functions for each field on each type:

function Query_me(request) {
  return request.auth.user;
}

function User_name(user) {
  return user.getName();
}

Once the service is running - it can receive graphQL queries to validate and execute.

{
  me {
    name
  }
}

Could return:

{
  "me": {
    "name": "Luke Skywalker"
  }
}

What is Graphene?#

  • Graphene is a library that provides tools to implement graphQL in python
  • Uses a code first approach
  • Works with most frameworks and ORMs
  • Instead of writing GraphQL Schema Definition Language (SDL) - we write python code

Install Graphene:

pip install "graphene>=3.0"

Create a basic schema:

from graphene import ObjectType, String, Schema

class Query(ObjectType):
    # this defines a Field `hello` in our Schema with a single Argument `name`
    hello = String(name=String(default_value="stranger"))
    goodbye = String()

    # our Resolver method takes the GraphQL context (root, info) as well as
    # Argument (name) for the Field and returns data for the query Response
    def resolve_hello(root, info, name):
        return f'Hello {name}!'

    def resolve_goodbye(root, info):
        return 'See ya!'

schema = Schema(query=Query)

The schema defines each field and type. Along with any arguments. Each field must have a resolver.

In the GraphQL schema definition language it would look like:

type Query {
  hello(name: String = "stranger"): String
  goodbye: String
}

Example request:

{
  hello(name: "friend")
}

Example response:

{
  "data": {
    "hello": "Hello friend!"
  }
}

Querying:

# we can query for our field (with the default argument)
query_string = '{ hello }'
result = schema.execute(query_string)
print(result.data['hello'])
# "Hello stranger!"

# or passing the argument in the query
query_with_argument = '{ hello(name: "GraphQL") }'
result = schema.execute(query_with_argument)
print(result.data['hello'])
# "Hello GraphQL!"

Integrations:

Sources#