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GraphQL-core 3 is a Python 3.6+ port ofGraphQL.js,the JavaScript reference implementation forGraphQL,a query language for APIs created by Facebook.

The current version 3.2.0 of GraphQL-core is up-to-date with GraphQL.js version 16.2.0.

An extensive test suite with over 2300 unit tests and 100% coverage comprises areplication of the complete test suite of GraphQL.js, making sure this port isreliable and compatible with GraphQL.js.

Note that for various reasons, GraphQL-core does not use SemVer like GraphQL.js. Increases in the major version of GraphQL.js are reflected in the minor version of GraphQL-core instead. This means there can be breaking changes in the API when the minor version changes, and only patch releases are fully backward compatible. Therefore, we recommend something like=~ 3.2.0 as version specifier when including GraphQL-core as a dependency.

A more detailed documentation for GraphQL-core 3 can be found atgraphql-core-3.readthedocs.io.

The documentation for GraphQL.js can be found atgraphql.org/graphql-js/.

The documentation for GraphQL itself can be found atgraphql.org.

There will be alsoblog articles with more usageexamples.

A general overview of GraphQL is available in theREADME for theSpecification for GraphQL. That overviewdescribes a simple set of GraphQL examples that exist astests in thisrepository. A good way to get started with this repository is to walk through thatREADME and the corresponding tests in parallel.

GraphQL-core 3 can be installed from PyPI using the built-in pip command:

python -m pip install graphql-core

You can also usepipenv for installation in avirtual environment:

pipenv install graphql-core

GraphQL-core provides two important capabilities: building a type schema andserving queries against that type schema.

First, build a GraphQL type schema which maps to your codebase:

fromgraphqlimport (GraphQLSchema,GraphQLObjectType,GraphQLField,GraphQLString)schema=GraphQLSchema(query=GraphQLObjectType(name='RootQueryType',fields={'hello':GraphQLField(GraphQLString,resolve=lambdaobj,info:'world')        }))

This defines a simple schema, with one type and one field, that resolves to a fixedvalue. Theresolve function can return a value, a co-routine object or a list ofthese. It takes two positional arguments; the first one provides the root or theresolved parent field, the second one provides aGraphQLResolveInfo object whichcontains information about the execution state of the query, including acontextattribute holding per-request state such as authentication information or databasesession. Any GraphQL arguments are passed to theresolve functions as individualkeyword arguments.

Note that the signature of the resolver functions is a bit different in GraphQL.js,where the context is passed separately and arguments are passed as a single object.Also note that GraphQL fields must be passed as aGraphQLField object explicitly.Similarly, GraphQL arguments must be passed asGraphQLArgument objects.

A more complex example is included in the top-leveltests directory.

Then, serve the result of a query against that type schema.

fromgraphqlimportgraphql_syncsource='{ hello }'print(graphql_sync(schema,source))

This runs a query fetching the one field defined, and then prints the result:

ExecutionResult(data={'hello':'world'},errors=None)

Thegraphql_sync function will first ensure the query is syntactically andsemantically valid before executing it, reporting errors otherwise.

fromgraphqlimportgraphql_syncsource='{ BoyHowdy }'print(graphql_sync(schema,source))

Because we queried a non-existing field, we will get the following result:

ExecutionResult(data=None,errors=[GraphQLError("Cannot query field 'BoyHowdy' on type 'RootQueryType'.",locations=[SourceLocation(line=1,column=3)])])

Thegraphql_sync function assumes that all resolvers return values synchronously. Byusing coroutines as resolvers, you can also create results in an asynchronous fashionwith thegraphql function.

importasynciofromgraphqlimport (graphql,GraphQLSchema,GraphQLObjectType,GraphQLField,GraphQLString)asyncdefresolve_hello(obj,info):awaitasyncio.sleep(3)return'world'schema=GraphQLSchema(query=GraphQLObjectType(name='RootQueryType',fields={'hello':GraphQLField(GraphQLString,resolve=resolve_hello)        }))asyncdefmain():query='{ hello }'print('Fetching the result...')result=awaitgraphql(schema,query)print(result)asyncio.run(main())

GraphQL-core tries to reproduce the code of the reference implementation GraphQL.jsin Python as closely as possible and to stay up-to-date with the latest development ofGraphQL.js.

GraphQL-core 3 (formerly known as GraphQL-core-next) has been created as a modernalternative toGraphQL-core 2,a prior work by Syrus Akbary, based on an older version of GraphQL.js and alsotargeting older Python versions. Some parts of GraphQL-core 3 have been inspired byGraphQL-core 2 or directly taken over with only slight modifications, but most of thecode has been re-implemented from scratch, replicating the latest code in GraphQL.jsvery closely and adding type hints for Python.

Design goals for the GraphQL-core 3 library were:

• to be a simple, cruft-free, state-of-the-art GraphQL implementation for currentPython versions
• to be very close to the GraphQL.js reference implementation, while still providinga Pythonic API and code style
• to make extensive use of Python type hints, similar to how GraphQL.js used Flow(and is now using TypeScript)
• to useblack to achieve a consistent code stylewhile saving time and mental energy for more important matters
• to replicate the complete Mocha-based test suite of GraphQL.jsusingpytestwithpytest-describe

Some restrictions (mostly in line with the design goals):

• requires Python 3.6 or newer
• does not support some already deprecated methods and options of GraphQL.js
• supports asynchronous operations only via async.io(does not support the additional executors in GraphQL-core)

• Graphene is a more high-level framework for buildingGraphQL APIs in Python, and there is already a whole ecosystem of libraries, serverintegrations and tools built on top of Graphene. Most of this Graphene ecosystem hasalso been created by Syrus Akbary, who meanwhile has handed over the maintenanceand future development to members of the GraphQL-Python community.

  The current version 2 of Graphene is using Graphql-core 2 as core library for much ofthe heavy lifting. Note that Graphene 2 is not compatible with GraphQL-core 3.The new version 3 of Graphene will use GraphQL-core 3 instead of GraphQL-core 2.

• Ariadne is a Python library for implementingGraphQL servers using schema-first approach created by Mirumee Software.

  Ariadne is already using GraphQL-core 3 as its GraphQL implementation.

• Strawberry, created by PatrickArminio, is a new GraphQL library for Python 3, inspired by dataclasses,that is also using GraphQL-core 3 as underpinning.

Changes are tracked asGitHub releases.

The GraphQL-core 3 library

• has been created and is maintained by Christoph Zwerschke
• uses ideas and code from GraphQL-core 2, a prior work by Syrus Akbary
• is a Python port of GraphQL.js which has been developed by Lee Byron and othersat Facebook, Inc. and is now maintainedby theGraphQL foundation

Please watch the recording of Lee Byron's short keynote on thehistory of GraphQLat the open source leadership summit 2019 to better understandhow and why GraphQL was created at Facebook and then became open sourcedand ported to many different programming languages.

GraphQL-core 3 isMIT-licensed,just like GraphQL.js.