jsonschema is an implementation of JSON Schema for Python (supporting 2.6+ including Python 3).

>>> 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({"name" : "Eggs", "price" : 34.99}, schema)

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

• Full support for Draft 3 and Draft 4 of the schema.
• Lazy validation that can iteratively report all validation errors.
• Small and extensible
• Programmatic querying of which properties or items failed validation.

v1.0.0 is a new major release of jsonschema.

It includes two major new features: support for the newly released draft 4 of the specification (thanks to Chase Sterling) and optional support for format (thanks to Norman Hooper).

It also contains two major backwards incompatible changes: draft 4 is now the default for schemas without $schema specified, and ValidationErrors now have path in sequential order.

It also fixes a minor issue with longs not being recognized as integers and a number of issues with the support for $ref.

Also, ValidatorMixin can be used to construct concrete validators for users who wish to create their own from scratch.

As always, see the documentation for details.

v1.1.0 fixes a bug whereby URIs were not canonicalized when stored and looked up (#70) and also allows for registering exceptions that can be accessed from ValidationErrors when validating format properties (#77).

jsonschema uses the wonderful Tox for its test suite. (It really is wonderful, if for some reason you haven't heard of it, you really should use it for your projects).

Assuming you have tox installed (perhaps via pip install tox or your package manager), just run tox in the directory of your source checkout to run jsonschema's test suite on all of the versions of Python jsonschema supports. Note that you'll need to have all of those versions installed in order to run the tests on each of them, otherwise tox will skip (and fail) the tests on that version.

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!

You can also generally find me on Freenode (nick: tos9) in various channels, including #python.