pekkaklarck/argtypes

Decorator for argument type verification and conversion

This module provides argtypes decorator that can verify argument types of Python functions and convert arguments to expected types. The main usage is with Robot Framework test libraries that want to verify/convert arguments their keywords accept.

Requires wrapt that can be installed with:

pip install wrapt

Examples

Basic argument type checking and conversion:

from argtypes import argtypes

class MyClass(object):
    pass

@argtypes(MyClass)
 def func(arg):
    assert isinstance(arg, MyClass)

func(MyClass())

@argtypes(int, arg2=str, arg3=bool)
def func2(arg1, arg2, arg3=True):
    assert isinstance(arg1, int)
    assert isinstance(arg2, str)
    assert isinstance(arg3, bool)

func2(42, 42)
func2(arg1='1', arg2=2, arg3='False')

Registering custom converters:

from argtypes import argtypes

class MyClass(object):
    def __init__(self, value):
        self.value = value

@argtypes(MyClass)
def func(arg):
    return arg

argtypes.register_converter(MyClass)
assert func(42).value == 42

argtypes.register_converter(MyClass, lambda arg: MyClass(arg*2))
assert func(42).value == 84

argtypes.unregister_converter(MyClass)