>>> 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'

Features

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.

Release Notes

v1.3.0 adds better, more verbose tracebacks for validation errors that give some actual possibility of seeing what went wrong, particularly for the new anyOf, oneOf and allOf validators in draft 4.

The other notable change is that ErrorTrees now raise exceptions for keys that aren't in the instance, to prevent typos.

__cause__ is also implemented on Py3 for format errors, if that floats your boat.

Running the Test Suite

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.

Community

There's a mailing list for this implementation on Google Groups.

Please join, and feel free to send questions there.

Contributing

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.