class_with_str.py

def class_with_str(class_name, module_name):
    """
    Returns a class object with the provided `class_name` in the scope of the `module_name`.
    """

    try:
        class_ = reduce(getattr, class_name.split("."), sys.modules[module_name])
    except AttributeError:
        raise NameError('Class "%s" does not exist!' % class_name)

    if (isinstance(class_var, (types.ClassType, types.TypeType))):
        return class_

    raise Exception('"%s" is not a class!' % class_name)