simple_type_checker

A small extendable python type checker library

Basic Usage

Checking a type:

from simple_type_check import type_check
assert type_check("A string", str)

As a decorator:

from simple_type_check import type_check, TypeCheckFailed

@type_check.returns
def id_(x) -> int:
    return x

_ = id_(1)  # Passes
try:
    _ = id_("string")  # Raises
except TypeCheckFailed as e:
    pass

Decorators for aruments exist as well: type_check.args. Both can be done at once with type_check.decorate.

With custom types

Basic types where isinstance is sufficient:

from simple_type_check import TypeChecker

class Foo:
    pass

type_check = TypeChecker(Foo)

assert type_check(Foo(), Foo)

Special type checking logic desired:

from simple_type_check import TopLevelCheck, TypeChecker

Bar = list[int] | list["Bar"]

class BarCheck(TopLevelCheck):
    def __call__(self, obj, type_) -> bool:
        return type_ == "Bar" and self._recurse(obj, Bar)

type_check = TypeChecker(advanced=[BarCheck])

type_check([1, [2], [[3]]], Bar)  # Should pass

This use case is useful for container types that take arguments, for example.