Crappy runtime typing for python

typing.py

import functools


class ArgumentLengthMismatchException(Exception):
    pass


class InvalidParameterTypeException(Exception):
    pass


def typed(*type_args):

    def decorator(func):

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            if len(args) != len(type_args):
                raise ArgumentLengthMismatchException(
                    "The number of arguments passed to function {func_name} did not match the number of types defined for it.".format(
                        func_name=func.func_name
                    )
                )

            for i, (arg, arg_type) in enumerate(zip(args, type_args)):
                if type(arg) != arg_type:
                    raise InvalidParameterTypeException(
                        "Argument {arg_number} passed to function {func_name} had type {actual_type}, but the type signature was {signature_type}".format(
                            arg_number=i, 
                            func_name=func.func_name, 
                            actual_type=type(arg), 
                            signature_type=arg_type
                        )
                    )
            return func(*args, **kwargs)

        return wrapper

    return decorator


@typed(int, int)
def add(a, b):
    return a + b


# In [1]: add(1, 2)
# Out[1]: 3
# 
# In [2]: add(1, 1, 1)
# ---------------------------------------------------------------------------
# ArgumentLengthMismatchException           Traceback (most recent call last)
# <ipython-input-367789e5329c> in <module>()
# ----> 1 add(1, 1, 1)
# 
# <ipython-input-21042874bf6a> in wrapper(*args, **kwargs)
#      16                 raise ArgumentLengthMismatchException(
#      17                     "The number of arguments passed to function {func_name} did not match the number of types defined for it.".format(
# ---> 18                         func_name=func.func_name
#      19                     )
#      20                 )
# 
# ArgumentLengthMismatchException: The number of arguments passed to function add did not match the number of types defined for it.
# 
# In [3]: add(1, '2')
# ---------------------------------------------------------------------------
# InvalidParameterTypeException             Traceback (most recent call last)
# <ipython-input-bc3442d797f0> in <module>()
# ----> 1 add(1, '2')
# 
# <ipython-input-21042874bf6a> in wrapper(*args, **kwargs)
#      27                             func_name=func.func_name,
#      28                             actual_type=type(arg),
# ---> 29                             signature_type=arg_type
#      30                         )
#      31                     )
# 
# InvalidParameterTypeException: Argument 1 passed to function add had type <type 'str'>, but the type signature was <type 'int'>