def derive_param_default(obj_param):
    """Derive a parameter default

    Parameters
    ----------
    obj_param : dict
        * parameter dict from TaniumPy object

    Returns
    -------
    def_val : str
        * default value derived from obj_param
    """
    # get the default value for this param if it exists
    def_val = obj_param.get('defaultValue', '')

    # get requireSelection for this param if it exists (pulldown menus)
    req_sel = obj_param.get('requireSelection', False)

    # get values for this param if it exists (pulldown menus)
    values = obj_param.get('values', [])

    # if this param requires a selection and it has a list of values
    # and there is no default value, use the first value as the
    # default value
    if req_sel and values and not def_val:
        def_val = values[0]
    return def_val