def user_index_by_id(slack_id, users):
    """
        Returns index of user in users list, based on it's Slack id
        :param slack_id:
        :param users:
        :return: Index in users or False
    """

    found_users = [user for user in users if user['id'] == slack_id]
    if len(found_users) == 0:
        # not found
        return False
    elif len(found_users) == 1:
        return users.index(found_users[0])
    else:
        # found more than one, this should never happen
        return False