Validation of incoming requests is a must-have for modern rest-like APIs.

• validate incoming JSON-Requests as defined by your colander schemas
• raise HTTP 400 (Bad request) if the request does not match your schema
• output readable error message in case of an invalid request
• stay out of your way in any other cases

You can simply install pyramid_request_schema via pip:

$ pip install pyramid_request_schema

You can either include pyramid_request_schema in your ini file

pyramid.includes =
    ...
    pyramid_request_schema
    ...

or programmatically in your main function

def main(global_config, **settings):
    config = Configurator(...)
    ...
    config.include("pyramid_request_schema")

Each of both includes does nothing but registering the view deriver schema_validated_view.

The usage of pyramid_request_schema is dead simple. Define a proper colander schema representing your expected input:

class TestRequestSchema(colander.MappingSchema):

    @colander.instantiate()
    class body(colander.MappingSchema):
        str_val = colander.SchemaNode(colander.String())
        float_val = colander.SchemaNode(colander.Float())

    @colander.instantiate()
    class queryset(colander.MappingSchema):
        page = colander.SchemaNode(colanger.Integer(),
                                   validator=colander.Range(1))

and add the request_schema option to your view configuration:

@view_config(request_schema=TestRequestSchema)
def my_view(request):
    pass

You can then access the validated data via the validated attribute on the request object. The resulting structure for the above defined schema and the following curl request will look like:

request.validated = {
    "body": {
        "str_val": "Some arbitrary string",
        "float_val": 12.34,
    },
    "queryset": {
        "page": 1
    }
}

$ curl -H "content-type: application/json" \
    --data='{"str_val": "Some arbitrary string", "float_val": "12.34"}' \
    http://example.com/?page=1