import inspect


def getargspec(obj):
    """Get the names and default values of a function's arguments.

    A tuple of four things is returned: (args, varargs, varkw, defaults).
    'args' is a list of the argument names (it may contain nested lists).
    'varargs' and 'varkw' are the names of the * and ** arguments or None.
    'defaults' is an n-tuple of the default values of the last n arguments.

    Modified version of inspect.getargspec from the Python Standard
    Library."""

    if inspect.isfunction(obj):
        func_obj = obj
    elif inspect.ismethod(obj):
        func_obj = obj.__func__
    else:
        raise TypeError('arg is not a Python function')
    args, varargs, varkw = inspect.getargs(func_obj.__code__)
    return args, varargs, varkw, func_obj.__defaults__