jsonschema is an implementation of the JSON Schema specification for Python.

>>> from jsonschema import validate

>>> # A sample schema, like what we'd get from json.load()
>>> schema = {
...     "type" : "object",
...     "properties" : {
...         "price" : {"type" : "number"},
...         "name" : {"type" : "string"},
...     },
... }

>>> # If no exception is raised by validate(), the instance is valid.
>>> validate(instance={"name" : "Eggs", "price" : 34.99}, schema=schema)

>>> validate(
...     instance={"name" : "Eggs", "price" : "Invalid"}, schema=schema,
... )                                   # doctest: +IGNORE_EXCEPTION_DETAIL
Traceback (most recent call last):
    ...
ValidationError: 'Invalid' is not of type 'number'

It can also be used from the command line by installing check-jsonschema.

• Full support for Draft 2020-12, Draft 2019-09, Draft 7, Draft 6, Draft 4 and Draft 3
• Lazy validation that can iteratively report all validation errors.
• Programmatic querying of which properties or items failed validation.

jsonschema is available on PyPI. You can install using pip:

$ pip install jsonschema

Two extras are available when installing the package, both currently related to format validation:

• format
• format-nongpl

They can be used when installing in order to include additional dependencies, e.g.:

$ pip install jsonschema'[format]'

Be aware that the mere presence of these dependencies – or even the specification of format checks in a schema – do not activate format checks (as per the specification). Please read the format validation documentation for further details.

If you have nox installed (perhaps via pipx install nox or your package manager), running nox in the directory of your source checkout will run jsonschema's test suite on all of the versions of Python jsonschema supports. If you don't have all of the versions that jsonschema is tested under, you'll likely want to run using nox's --no-error-on-missing-interpreters option.

Of course you're also free to just run the tests on a single version with your favorite test runner. The tests live in the jsonschema.tests package.

jsonschema's benchmarks make use of pyperf. Running them can be done via:

$ nox -s perf

The JSON Schema specification has a Slack, with an invite link on its home page. Many folks knowledgeable on authoring schemas can be found there.

Otherwise, opening a GitHub discussion or asking questions on Stack Overflow are other means of getting help if you're stuck.

I'm Julian Berman.

jsonschema is on GitHub.

Get in touch, via GitHub or otherwise, if you've got something to contribute, it'd be most welcome!

If you feel overwhelmingly grateful, you can also sponsor me.

And for companies who appreciate jsonschema and its continued support and growth, jsonschema is also now supportable via TideLift.