runchecker

A dynamic, runtime type checker for Python 3.7+!

Example

>>> import runchecker
>>> @runchecker.check
... def hey_there(name: str, greeting: str) -> str:
... return greeting + " " + name + "!"
...
>>> hey_there("John", "Hello")
"Hello John!"
>>> hey_there(487, "Hello")
Traceback (most recent call last):
 ...
runchecker.errors.InvalidParameter: Parameter name with value 487 (type int) is incompatible with str!

What Currently Works

runchecker currently supports the following type hints:

• object
• Any
• None
• collections.abc.Mapping
• collections.abc.Sequence
• tuple
• Union
• Generic
• TypedDict
• Literal
• Annotated

runchecker plans to support the following type hints in the future:

• TypeVar
• Forward References
• and more to come!

Validating a Custom Generic

If you have a custom Generic class that doesn't follow any of the protocols runchecker currently supports, no problem!

runchecker allows you to make a custom validator for your custom Generic class. Instance checks will already be done for you automatically.

All you have to do is inherit from runchecker.Validator, which is a protocol class that defines a dunder function (not method) called __validate__.

__validate__ takes in two parameters: the type_hint (typed as Any) and the value (typed as Any). The type_hint will be the type hint that called this validator, and the value will be the value to validate.

__validate__ has a return type of anything. All you have to do in your __validate__ implementation is raise runchecker.WrongType if the value parameter violates type_hint!

Licensing

runchecker is licensed under the MIT License. Read the LICENSE file for more information.