supersergiy / typeguard

Run-time type checker for Python

This library provides run-time type checking for functions defined with PEP 484 argument (and return) type annotations, and any arbitrary objects. It can be used together with static type checkers as an additional layer of type safety, to catch type violations that could only be detected at run time.

Four principal ways to do type checking are provided, each with its pros and cons:

1. The check_type function:
   • like isinstance(), but supports arbitrary type annotations (within limits)
   • can be used as a cast() replacement, but with actual checking of the value
2. the check_argument_types() and check_return_type() functions:
   • debugger friendly (except when running with the pydev debugger with the C extension installed)
   • does not work reliably with dynamically defined type hints (e.g. in nested functions)
3. the @typechecked decorator:
   • automatically type checks yields and sends of returned generators (regular and async)
   • adds an extra frame to the call stack for every call to a decorated function
4. the import hook (typeguard.importhook.install_import_hook()):
   • automatically instruments targeted modules on import
   • no manual code changes required in the target modules
   • requires the import hook to be installed before the targeted modules are imported
   • may clash with other import hooks

See the documentation for further information.