typeguards 0.2.0

Utilities to help with type checking.

This is a Python library of TypeGuard functions that can be used for static type narrowing, and runtime type checking.

is_json(
    {
        "str_key": "str_val",
        "int_key": 1,
        "float_key": 1.0,
        "bool_key": True,
        "none_key": None,
        "list_key": [1, 2, "3", {"foo": "bar"}],
        "dict_key": {"foo": "bar"},
    },
)  # True

Installation

pip install typeguards

Usage

Assert that an object is valid JSON.

from typeguards.json import is_json

assert is_json(
    {
        "str_key": "str_val",
        "int_key": 1,
        "float_key": 1.0,
        "bool_key": True,
        "none_key": None,
        "list_key": [1, 2, "3", {"foo": "bar"}],
        "dict_key": {  # dict values can be nested infinitely
                "foo": "bar",
        },
    },
)  # OK

assert is_json("a string")  # AssertionError
assert is_json([1, 2, 3])  # AssertionError

Assert that an object conforms to a JSON schema.

from typing import List, NamedTuple, TypedDict

from typeguards.json import is_json_schema


class HobbySchema(NamedTuple):
   name: str
   is_fun: bool


class UserSchema(TypedDict):
   id: int
   username: str
   hobbies: List[HobbySchema]  # Nested schema


assert is_json_schema(
    {
        "id": 7,
        "username": "charlotte",
        "hobbies": [{"name": "Hyrule Warriors: Age of Calamity", "is_fun": True}],
    },
    UserSchema,
)  # OK

assert is_json_schema(
    {
        # No id, but still conforms to schema
        "username": "oscar",
        "hobbies": [{"name": "Whacking things", "is_fun": True}],
    },
    UserSchema,
)  # OK

assert is_json_schema(
    {
        "bad-id": 123,  # Doesn't conform to schema
        "username": "narvin",
        "hobbies": [{"name": "Watching coding videos", "is_fun": False}],
    },
    UserSchema,
)  # AssertionError