Trivial validation - when the full power of the JSON Schema is not needed

This library provides a simplistic way to validate a dictionary against something resembling a schema - a dictionary describing the desired data structure by example.

The main entry point is the validate() function, but the various validate_*() functions may be invoked directly with appropriate arguments.

The schema used for validation is a dictionary (the top-level object must be a dictionary). For the present, the keys may only be strings. A special case of a dictionary with a single key * means any value for a key will be accepted. Otherwise, all keys with names not starting with a ? character are mandatory, and any keys with names starting with a ? character are optional.

The dictionary values may be any of:

• a Python type signifying that the value must be an instance thereof
• a single-element list signifying that the value must be a list with all the elements validated by the same rules as a dictionary value (i.e. one of a Python type, a single-element list, a set, or a dictionary)
• a set signifying that the value must be exactly equal to one of the set elements, i.e. an enumeration of the allowed values
• a dictionary with the same semantics as described above

For example, the following schema:

{
    "name": str,
    "id": int,
    "address": [str],
    "preferences": {
        "meal": set(("breakfast", "lunch", "brunch")),
        "colors": [{
            "name": str,
            "intensity": set(["dark", "light"])
        }]
    },
    "possessions": {
        "*": int
    }
}

...may be used to validate the following dictionary:

{
    "name": "A. N. Nymous",
    "id": 13,
    "address": [
        "42 Nowhere Circle",
        "Notown-at-all",
        "Unnamed territory"
    ],
    "preferences": {
        "meal": "brunch",
        "colors": [
            {"name": "blue", "intensity": "light"},
            {"name": "green", "intensity": "dark"}
        ]
    },
    "possessions": {
        "pencil": 4,
        "paper": 0
    }
}