>>> 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 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

v0.7 introduces a number of changes.

The most important one is that the Validator class is now deprecated.

In its place is the Draft3Validator class (soon to be accompanied by others for other supported versions). This class accepts a schema when initializing, so that the new interface is:

validator = Draft3Validator(my_schema)
validator.validate(some_instance)

Also, no meta-validation is done. If you want to check if a schema is valid, use the check_schema classmethod (i.e. use Draft3Validator.check_schema(a_maybe_valid_schema)).

The validate function of course still exists and continues to work as it did before:

from jsonschema import validate
validate(my_instance, my_schema)

There's just one exception: the meta_validate argument is deprecated, and meta-validation will now always be done. If you don't want to have it done, construct a validator directly as above.

One last thing that is present is partial support for $ref, at least for JSON Pointer refs. Full support should be coming soon.

As always, if you find any bugs, please file a ticket.

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.

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.