Jsonism - The Simple Python JSON Checker

A super-simple library for validating JSON against a schema.

Install from pip

pip install jsonism

Why use Jsonism?

Jsonism is a great alternative to jsonschema when you just want to do some simple validation of JSON without your code getting horrendously complicated.

It's quick to set up a basic schema checker.

Example usage

Import the checker

from jsonism.checker import validate

The validate function returns True if the input you give it matches the schema that you provide.

Basic flat objects

schema = {
    "Bob": str,
    "Lucy": int,
    "Bert": bool
}
input = {
    "Bob": "Is Bob",
    "Lucy": 13,
    "Bert": True
}
validate(input, schema)

Lists

input = ["Bob", "Alice", "John"]
schema = [str]
validate(input, schema)

Other stuff

input = {"Usernames": [{"username": "Bob", "age": 23}, {"username": "Bill", "age": 98}]}
schema = {"Usernames": [{"username": str, "age": int}]}
validate(input, schema)

Obviously for more complex json, you can json.loads the input.

Permissive validation

Jsonism is permissive when it comes to extra elements. As long as the elements listed in the schema are provided, validate will return True. If additional elements are added to the input, validate will still return True.

schema = {
    "Bob": str,
    "Lucy": int,
    "Bert": bool
}
input = {
    "Bob": "Is Bob",
    "Lucy": 13,
    "Bert": True,
    "Colin": 21
}
validate(input, schema)  # Will return True

Value validation

This is absolutely optional, in order to keep things as simple as possible and enable the use of the in-built types int, str, bool, and float wherever possible. But we do also support the use of value validation as follows:

from jsonism.checker import validate
from jsonism.types import String, Integer, Boolean, Float

schema = {
    "Bob": String(len=6),
    "Lucy": Integer(max=96),
    "Bert": Boolean(allowed=True),
    "Chris": Float(min=12.34)
}
input = {
    "Bob": "Is Bob",
    "Lucy": 30,
    "Bert": True,
    "Chris": 34.2
}
validate(input, schema)  # Will return True

Lists of valid values

from jsonism.checker import validate
from jsonism.types import String, Integer, Boolean, Float

schema = {
    "Bob": String(options=["Is Bob", "Not Bob"]),
    "Lucy": Integer(max=22),
    "Bert": Boolean(allowed=True)
}
input = {
    "Bob": "Was Bob",
    "Lucy": 22,
    "Bert": True
}
validate(input, schema)  # Will return False

But it doesn't have feature x!

Well, I did say it was simple. It will always support the very simple initialisation shown above. We also now support value validation. If you have a burning desire to add a feature, please either post an issue or make a pull request at https://github.com/bmcollier/jsonism.