def sort_list_of_dicts(list_, dict_key):
    """Sort list of dicts by dict key

    :param list list_: List of dicts,
    :param string dict_key: Dict key for sorting.
    :rtype: list
    """
    items = []
    for item in list_:
        if item[dict_key] is None:
            item[dict_key] = str()
        items.append(item)
    return sorted(items, key=lambda item: item[dict_key])
