我的这段代码在json文件中为用户添加了50个点，但是'dict' object has no attribute 'append'在尝试将新用户追加到用户时却不断出现：

def updateUsers(chan):
    j = urllib2.urlopen('http://tmi.twitch.tv/group/user/' + chan + '/chatters')
    j_obj = json.load(j)
    with open('dat.dat', 'r') as data_file:
        data = json.load(data_file)
        for dat in data['users']:
            if dat in j_obj['chatters']['moderators'] or j_obj['chatters']['viewers']:
                data['users']['tryhard_cupcake']['Points'] += 50
            else:
                data['users'].append([dat]) # append doesn't work here
    with open('dat.dat', 'w') as out_file:
        json.dump(data, out_file)

向其添加新对象/用户的正确方法是users什么？